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	$221.70	13.655%	$251.9731	$251.97	$251.95	$252.00
Purchase #2	$76.35	3.421%	$78.9619	$78.96	$78.95	$79.00
Purchase #3	$55.35	6.752%	$59.0872	$59.09	$59.10	$59.10
Purchase #4	$229.63	8.559%	$249.284	$249.28	$249.30	$249.30
Purchase #5	$105.55	5.809%	$111.6814	$111.68	$111.70	$111.70
Purchase #6	$91.87	3.502%	$95.0873	$95.09	$95.10	$95.10
Purchase #7	$89.97	12.700%	$101.3962	$101.40	$101.40	$101.40
7 purchase totals =	$870.42		$947.4711	$947.47	$947.50	$947.60