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	$39.74	4.281%	$41.4413	$41.44	$41.45	$41.40
Purchase #2	$10.86	7.758%	$11.7025	$11.70	$11.70	$11.70
Purchase #3	$116.91	12.720%	$131.781	$131.78	$131.80	$131.80
Purchase #4	$37.94	12.547%	$42.7003	$42.70	$42.70	$42.70
Purchase #5	$115.33	13.119%	$130.4601	$130.46	$130.45	$130.50
Purchase #6	$47.98	4.656%	$50.2139	$50.21	$50.20	$50.20
Purchase #7	$41.47	6.231%	$44.054	$44.05	$44.05	$44.10
7 purchase totals =	$410.23		$452.3531	$452.34	$452.35	$452.40