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	$22.44	11.114%	$24.934	$24.93	$24.95	$24.90
Purchase #2	$76.91	6.187%	$81.6684	$81.67	$81.65	$81.70
Purchase #3	$36.25	10.753%	$40.148	$40.15	$40.15	$40.10
Purchase #4	$223.36	7.530%	$240.179	$240.18	$240.20	$240.20
Purchase #5	$174.74	11.635%	$195.071	$195.07	$195.05	$195.10
Purchase #6	$73.92	6.242%	$78.5341	$78.53	$78.55	$78.50
Purchase #7	$40.27	13.769%	$45.8148	$45.81	$45.80	$45.80
7 purchase totals =	$647.89		$706.3493	$706.34	$706.35	$706.30