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	$90.49	12.797%	$102.07	$102.07	$102.05	$102.10
Purchase #2	$250.94	5.475%	$264.679	$264.68	$264.70	$264.70
Purchase #3	$97.34	7.765%	$104.8985	$104.90	$104.90	$104.90
Purchase #4	$231.46	7.787%	$249.4838	$249.48	$249.50	$249.50
Purchase #5	$110.91	12.394%	$124.6562	$124.66	$124.65	$124.70
Purchase #6	$208.72	11.848%	$233.4491	$233.45	$233.45	$233.40
Purchase #7	$100.25	11.461%	$111.7397	$111.74	$111.75	$111.70
7 purchase totals =	$1,090.11		$1,190.9763	$1,190.98	$1,191.00	$1,191.00