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	$93.40	13.404%	$105.9193	$105.92	$105.90	$105.90
Purchase #2	$82.35	11.449%	$91.7783	$91.78	$91.80	$91.80
Purchase #3	$206.37	8.847%	$224.6276	$224.63	$224.65	$224.60
Purchase #4	$209.47	9.555%	$229.4849	$229.48	$229.50	$229.50
Purchase #5	$112.50	3.565%	$116.5106	$116.51	$116.50	$116.50
Purchase #6	$217.81	5.809%	$230.4626	$230.46	$230.45	$230.50
Purchase #7	$50.85	6.643%	$54.228	$54.23	$54.25	$54.20
7 purchase totals =	$972.75		$1,053.0113	$1,053.01	$1,053.05	$1,053.00