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	$211.95	11.242%	$235.7774	$235.78	$235.80	$235.80
Purchase #2	$65.50	10.417%	$72.3231	$72.32	$72.30	$72.30
Purchase #3	$37.42	9.714%	$41.055	$41.06	$41.05	$41.10
Purchase #4	$152.69	8.622%	$165.8549	$165.85	$165.85	$165.90
Purchase #5	$112.25	12.541%	$126.3273	$126.33	$126.35	$126.30
Purchase #6	$216.84	7.200%	$232.4525	$232.45	$232.45	$232.50
Purchase #7	$123.59	8.330%	$133.885	$133.89	$133.90	$133.90
7 purchase totals =	$920.24		$1,007.6752	$1,007.68	$1,007.70	$1,007.80