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	$83.70	3.480%	$86.6128	$86.61	$86.60	$86.60
Purchase #2	$151.99	10.873%	$168.5159	$168.52	$168.50	$168.50
Purchase #3	$195.83	6.261%	$208.0909	$208.09	$208.10	$208.10
Purchase #4	$88.70	7.782%	$95.6026	$95.60	$95.60	$95.60
Purchase #5	$110.30	12.251%	$123.8129	$123.81	$123.80	$123.80
Purchase #6	$168.37	7.653%	$181.2554	$181.26	$181.25	$181.30
Purchase #7	$177.29	4.144%	$184.6369	$184.64	$184.65	$184.60
7 purchase totals =	$976.18		$1,048.5274	$1,048.53	$1,048.50	$1,048.50