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	$34.48	9.302%	$37.6873	$37.69	$37.70	$37.70
Purchase #2	$111.83	10.824%	$123.9345	$123.93	$123.95	$123.90
Purchase #3	$99.74	9.559%	$109.2741	$109.27	$109.25	$109.30
Purchase #4	$27.58	12.425%	$31.0068	$31.01	$31.00	$31.00
Purchase #5	$61.91	6.869%	$66.1626	$66.16	$66.15	$66.20
Purchase #6	$36.28	11.592%	$40.4856	$40.49	$40.50	$40.50
Purchase #7	$32.42	10.364%	$35.78	$35.78	$35.80	$35.80
7 purchase totals =	$404.24		$444.3309	$444.33	$444.35	$444.40