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	$221.32	4.668%	$231.6512	$231.65	$231.65	$231.70
Purchase #2	$124.72	4.502%	$130.3349	$130.33	$130.35	$130.30
Purchase #3	$249.46	10.202%	$274.9099	$274.91	$274.90	$274.90
Purchase #4	$140.69	4.326%	$146.7762	$146.78	$146.80	$146.80
Purchase #5	$39.98	13.604%	$45.4189	$45.42	$45.40	$45.40
Purchase #6	$75.41	13.329%	$85.4614	$85.46	$85.45	$85.50
Purchase #7	$234.71	5.830%	$248.3936	$248.39	$248.40	$248.40
7 purchase totals =	$1,086.29		$1,162.9461	$1,162.94	$1,162.95	$1,163.00