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	$176.33	8.763%	$191.7818	$191.78	$191.80	$191.80
Purchase #2	$81.92	8.356%	$88.7652	$88.77	$88.75	$88.80
Purchase #3	$76.75	7.241%	$82.3075	$82.31	$82.30	$82.30
Purchase #4	$62.70	4.270%	$65.3773	$65.38	$65.40	$65.40
Purchase #5	$240.30	5.363%	$253.1873	$253.19	$253.20	$253.20
Purchase #6	$101.90	3.656%	$105.6255	$105.63	$105.65	$105.60
Purchase #7	$139.70	8.367%	$151.3887	$151.39	$151.40	$151.40
7 purchase totals =	$879.60		$938.4333	$938.45	$938.50	$938.50