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	$102.46	12.313%	$115.0759	$115.08	$115.10	$115.10
Purchase #2	$128.25	8.434%	$139.0666	$139.07	$139.05	$139.10
Purchase #3	$129.97	4.741%	$136.1319	$136.13	$136.15	$136.10
Purchase #4	$205.43	11.820%	$229.7118	$229.71	$229.70	$229.70
Purchase #5	$50.75	4.441%	$53.0038	$53.00	$53.00	$53.00
Purchase #6	$221.90	10.192%	$244.516	$244.52	$244.50	$244.50
Purchase #7	$90.79	8.554%	$98.5562	$98.56	$98.55	$98.60
7 purchase totals =	$929.55		$1,016.0622	$1,016.07	$1,016.05	$1,016.10