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	$48.44	8.246%	$52.4344	$52.43	$52.45	$52.40
Purchase #2	$61.75	13.179%	$69.888	$69.89	$69.90	$69.90
Purchase #3	$97.61	11.767%	$109.0958	$109.10	$109.10	$109.10
Purchase #4	$233.30	7.299%	$250.3286	$250.33	$250.35	$250.30
Purchase #5	$189.30	13.482%	$214.8214	$214.82	$214.80	$214.80
Purchase #6	$41.59	10.869%	$46.1104	$46.11	$46.10	$46.10
Purchase #7	$131.72	11.550%	$146.9337	$146.93	$146.95	$146.90
7 purchase totals =	$803.71		$889.6123	$889.61	$889.65	$889.50