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	$209.29	12.298%	$235.0285	$235.03	$235.05	$235.00
Purchase #2	$242.81	10.590%	$268.5236	$268.52	$268.50	$268.50
Purchase #3	$232.46	11.713%	$259.688	$259.69	$259.70	$259.70
Purchase #4	$67.31	9.636%	$73.796	$73.80	$73.80	$73.80
Purchase #5	$57.80	11.661%	$64.5401	$64.54	$64.55	$64.50
Purchase #6	$45.69	11.339%	$50.8708	$50.87	$50.85	$50.90
Purchase #7	$104.62	6.549%	$111.4716	$111.47	$111.45	$111.50
7 purchase totals =	$959.98		$1,063.9186	$1,063.92	$1,063.90	$1,063.90