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	$56.98	13.260%	$64.5355	$64.54	$64.55	$64.50
Purchase #2	$175.77	12.599%	$197.9153	$197.92	$197.90	$197.90
Purchase #3	$58.52	10.822%	$64.853	$64.85	$64.85	$64.90
Purchase #4	$114.51	7.543%	$123.1475	$123.15	$123.15	$123.10
Purchase #5	$40.31	3.840%	$41.8579	$41.86	$41.85	$41.90
Purchase #6	$167.26	7.696%	$180.1323	$180.13	$180.15	$180.10
Purchase #7	$58.54	7.155%	$62.7285	$62.73	$62.75	$62.70
7 purchase totals =	$671.89		$735.1700	$735.18	$735.20	$735.10