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	$120.40	9.424%	$131.7465	$131.75	$131.75	$131.70
Purchase #2	$165.58	8.808%	$180.1643	$180.16	$180.15	$180.20
Purchase #3	$84.86	11.370%	$94.5086	$94.51	$94.50	$94.50
Purchase #4	$45.81	9.423%	$50.1267	$50.13	$50.15	$50.10
Purchase #5	$222.77	6.133%	$236.4325	$236.43	$236.45	$236.40
Purchase #6	$59.63	3.682%	$61.8256	$61.83	$61.85	$61.80
Purchase #7	$37.34	13.717%	$42.4619	$42.46	$42.45	$42.50
7 purchase totals =	$736.39		$797.2661	$797.27	$797.30	$797.20