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	$45.72	3.770%	$47.4436	$47.44	$47.45	$47.40
Purchase #2	$137.74	13.345%	$156.1214	$156.12	$156.10	$156.10
Purchase #3	$20.32	12.862%	$22.9336	$22.93	$22.95	$22.90
Purchase #4	$34.92	13.133%	$39.506	$39.51	$39.50	$39.50
Purchase #5	$67.90	7.419%	$72.9375	$72.94	$72.95	$72.90
Purchase #6	$28.64	9.395%	$31.3307	$31.33	$31.35	$31.30
Purchase #7	$221.90	9.704%	$243.4332	$243.43	$243.45	$243.40
7 purchase totals =	$557.14		$613.7060	$613.70	$613.75	$613.50