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	$196.30	3.615%	$203.3962	$203.40	$203.40	$203.40
Purchase #2	$239.51	12.382%	$269.1661	$269.17	$269.15	$269.20
Purchase #3	$146.55	4.208%	$152.7168	$152.72	$152.70	$152.70
Purchase #4	$82.72	3.668%	$85.7542	$85.75	$85.75	$85.80
Purchase #5	$191.31	6.359%	$203.4754	$203.48	$203.50	$203.50
Purchase #6	$136.85	11.705%	$152.8683	$152.87	$152.85	$152.90
Purchase #7	$64.39	10.602%	$71.2166	$71.22	$71.20	$71.20
7 purchase totals =	$1,057.63		$1,138.5936	$1,138.61	$1,138.55	$1,138.70