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	$161.41	13.319%	$182.9082	$182.91	$182.90	$182.90
Purchase #2	$176.86	8.459%	$191.8206	$191.82	$191.80	$191.80
Purchase #3	$152.71	4.566%	$159.6827	$159.68	$159.70	$159.70
Purchase #4	$78.89	5.439%	$83.1808	$83.18	$83.20	$83.20
Purchase #5	$91.76	12.626%	$103.3456	$103.35	$103.35	$103.30
Purchase #6	$18.61	11.165%	$20.6878	$20.69	$20.70	$20.70
Purchase #7	$100.61	13.191%	$113.8815	$113.88	$113.90	$113.90
7 purchase totals =	$780.85		$855.5072	$855.51	$855.55	$855.50