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	$172.46	8.695%	$187.4554	$187.46	$187.45	$187.50
Purchase #2	$49.48	10.600%	$54.7249	$54.72	$54.70	$54.70
Purchase #3	$52.71	3.349%	$54.4753	$54.48	$54.50	$54.50
Purchase #4	$98.81	13.634%	$112.2818	$112.28	$112.30	$112.30
Purchase #5	$155.76	5.624%	$164.5199	$164.52	$164.50	$164.50
Purchase #6	$178.36	7.248%	$191.2875	$191.29	$191.30	$191.30
Purchase #7	$105.55	5.850%	$111.7247	$111.72	$111.70	$111.70
7 purchase totals =	$813.13		$876.4695	$876.47	$876.45	$876.50