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	$174.45	5.719%	$184.4268	$184.43	$184.45	$184.40
Purchase #2	$212.98	9.510%	$233.2344	$233.23	$233.25	$233.20
Purchase #3	$215.85	4.127%	$224.7581	$224.76	$224.75	$224.80
Purchase #4	$48.91	8.439%	$53.0375	$53.04	$53.05	$53.00
Purchase #5	$120.72	4.483%	$126.1319	$126.13	$126.15	$126.10
Purchase #6	$10.49	12.412%	$11.792	$11.79	$11.80	$11.80
Purchase #7	$213.49	4.381%	$222.843	$222.84	$222.85	$222.80
7 purchase totals =	$996.89		$1,056.2237	$1,056.22	$1,056.30	$1,056.10