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	$184.76	13.614%	$209.9132	$209.91	$209.90	$209.90
Purchase #2	$82.64	13.118%	$93.4807	$93.48	$93.50	$93.50
Purchase #3	$108.31	5.780%	$114.5703	$114.57	$114.55	$114.60
Purchase #4	$159.73	3.108%	$164.6944	$164.69	$164.70	$164.70
Purchase #5	$210.75	8.617%	$228.9103	$228.91	$228.90	$228.90
Purchase #6	$40.87	4.178%	$42.5775	$42.58	$42.60	$42.60
Purchase #7	$219.50	3.492%	$227.1649	$227.16	$227.15	$227.20
7 purchase totals =	$1,006.56		$1,081.3113	$1,081.30	$1,081.30	$1,081.40