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	$161.63	4.418%	$168.7708	$168.77	$168.75	$168.80
Purchase #2	$42.52	3.319%	$43.9312	$43.93	$43.95	$43.90
Purchase #3	$178.65	10.142%	$196.7687	$196.77	$196.75	$196.80
Purchase #4	$15.96	10.764%	$17.6779	$17.68	$17.70	$17.70
Purchase #5	$172.50	11.506%	$192.3479	$192.35	$192.35	$192.30
Purchase #6	$62.91	6.766%	$67.1665	$67.17	$67.15	$67.20
Purchase #7	$243.38	7.585%	$261.8404	$261.84	$261.85	$261.80
7 purchase totals =	$877.55		$948.5034	$948.51	$948.50	$948.50