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	$71.85	9.178%	$78.4444	$78.44	$78.45	$78.40
Purchase #2	$11.33	4.369%	$11.825	$11.83	$11.85	$11.80
Purchase #3	$133.76	7.400%	$143.6582	$143.66	$143.65	$143.70
Purchase #4	$169.83	9.184%	$185.4272	$185.43	$185.45	$185.40
Purchase #5	$74.99	3.692%	$77.7586	$77.76	$77.75	$77.80
Purchase #6	$67.37	10.314%	$74.3185	$74.32	$74.30	$74.30
Purchase #7	$216.41	6.163%	$229.7473	$229.75	$229.75	$229.70
7 purchase totals =	$745.54		$801.1792	$801.19	$801.20	$801.10