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	$147.28	4.282%	$153.5865	$153.59	$153.60	$153.60
Purchase #2	$222.59	4.741%	$233.143	$233.14	$233.15	$233.10
Purchase #3	$85.63	10.807%	$94.884	$94.88	$94.90	$94.90
Purchase #4	$96.65	11.726%	$107.9832	$107.98	$108.00	$108.00
Purchase #5	$104.77	12.277%	$117.6326	$117.63	$117.65	$117.60
Purchase #6	$6.59	12.728%	$7.4288	$7.43	$7.45	$7.40
Purchase #7	$205.44	13.832%	$233.8565	$233.86	$233.85	$233.90
7 purchase totals =	$868.95		$948.5146	$948.51	$948.60	$948.50