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	$209.41	13.230%	$237.1149	$237.11	$237.10	$237.10
Purchase #2	$237.67	6.592%	$253.3372	$253.34	$253.35	$253.30
Purchase #3	$72.91	6.669%	$77.7724	$77.77	$77.75	$77.80
Purchase #4	$215.79	3.374%	$223.0708	$223.07	$223.05	$223.10
Purchase #5	$139.48	9.402%	$152.5939	$152.59	$152.60	$152.60
Purchase #6	$45.25	7.663%	$48.7175	$48.72	$48.70	$48.70
Purchase #7	$41.74	9.154%	$45.5609	$45.56	$45.55	$45.60
7 purchase totals =	$962.25		$1,038.1676	$1,038.16	$1,038.10	$1,038.20