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	$143.37	3.627%	$148.57	$148.57	$148.55	$148.60
Purchase #2	$59.32	13.265%	$67.1888	$67.19	$67.20	$67.20
Purchase #3	$80.65	11.819%	$90.182	$90.18	$90.20	$90.20
Purchase #4	$150.89	5.677%	$159.456	$159.46	$159.45	$159.50
Purchase #5	$180.95	5.624%	$191.1266	$191.13	$191.15	$191.10
Purchase #6	$41.38	13.771%	$47.0784	$47.08	$47.10	$47.10
Purchase #7	$70.34	7.186%	$75.3946	$75.39	$75.40	$75.40
7 purchase totals =	$726.90		$778.9964	$779.00	$779.05	$779.10