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	$82.67	12.331%	$92.864	$92.86	$92.85	$92.90
Purchase #2	$46.68	13.459%	$52.9627	$52.96	$52.95	$53.00
Purchase #3	$167.35	3.241%	$172.7738	$172.77	$172.75	$172.80
Purchase #4	$128.81	13.689%	$146.4428	$146.44	$146.45	$146.40
Purchase #5	$156.87	12.338%	$176.2246	$176.22	$176.20	$176.20
Purchase #6	$210.51	6.308%	$223.789	$223.79	$223.80	$223.80
Purchase #7	$35.78	6.141%	$37.9772	$37.98	$38.00	$38.00
7 purchase totals =	$828.67		$903.0341	$903.02	$903.00	$903.10