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	$86.79	5.694%	$91.7318	$91.73	$91.75	$91.70
Purchase #2	$247.31	6.801%	$264.1296	$264.13	$264.15	$264.10
Purchase #3	$152.38	12.609%	$171.5936	$171.59	$171.60	$171.60
Purchase #4	$63.89	11.859%	$71.4667	$71.47	$71.45	$71.50
Purchase #5	$69.89	11.199%	$77.717	$77.72	$77.70	$77.70
Purchase #6	$216.41	8.194%	$234.1426	$234.14	$234.15	$234.10
Purchase #7	$147.65	10.214%	$162.731	$162.73	$162.75	$162.70
7 purchase totals =	$984.32		$1,073.5123	$1,073.51	$1,073.55	$1,073.40