Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$180.70	4.681%	$189.1586	$189.16	$189.15	$189.20
Purchase #2	$114.79	5.242%	$120.8073	$120.81	$120.80	$120.80
Purchase #3	$243.67	10.423%	$269.0677	$269.07	$269.05	$269.10
Purchase #4	$172.79	13.585%	$196.2635	$196.26	$196.25	$196.30
Purchase #5	$159.32	5.831%	$168.6099	$168.61	$168.60	$168.60
Purchase #6	$189.75	10.626%	$209.9128	$209.91	$209.90	$209.90
Purchase #7	$192.31	8.429%	$208.5198	$208.52	$208.50	$208.50
7 purchase totals =	$1,253.33		$1,362.3396	$1,362.34	$1,362.25	$1,362.40