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	$71.38	9.717%	$78.316	$78.32	$78.30	$78.30
Purchase #2	$63.45	13.227%	$71.8425	$71.84	$71.85	$71.80
Purchase #3	$149.36	6.765%	$159.4642	$159.46	$159.45	$159.50
Purchase #4	$32.45	10.325%	$35.8005	$35.80	$35.80	$35.80
Purchase #5	$45.27	12.541%	$50.9473	$50.95	$50.95	$50.90
Purchase #6	$250.84	9.824%	$275.4825	$275.48	$275.50	$275.50
Purchase #7	$240.90	11.130%	$267.7122	$267.71	$267.70	$267.70
7 purchase totals =	$853.65		$939.5652	$939.56	$939.55	$939.50