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	$201.52	4.505%	$210.5985	$210.60	$210.60	$210.60
Purchase #2	$211.37	12.555%	$237.9075	$237.91	$237.90	$237.90
Purchase #3	$22.77	11.351%	$25.3546	$25.35	$25.35	$25.40
Purchase #4	$156.82	9.869%	$172.2966	$172.30	$172.30	$172.30
Purchase #5	$28.32	13.811%	$32.2313	$32.23	$32.25	$32.20
Purchase #6	$249.98	3.748%	$259.3493	$259.35	$259.35	$259.30
Purchase #7	$62.56	3.844%	$64.9648	$64.96	$64.95	$65.00
7 purchase totals =	$933.34		$1,002.7026	$1,002.70	$1,002.70	$1,002.70