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	$119.47	10.863%	$132.448	$132.45	$132.45	$132.40
Purchase #2	$34.57	13.742%	$39.3206	$39.32	$39.30	$39.30
Purchase #3	$235.97	8.272%	$255.4894	$255.49	$255.50	$255.50
Purchase #4	$226.99	10.199%	$250.1407	$250.14	$250.15	$250.10
Purchase #5	$210.77	12.504%	$237.1247	$237.12	$237.10	$237.10
Purchase #6	$54.41	9.256%	$59.4462	$59.45	$59.45	$59.40
Purchase #7	$27.47	3.832%	$28.5227	$28.52	$28.50	$28.50
7 purchase totals =	$909.65		$1,002.4923	$1,002.49	$1,002.45	$1,002.30