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	$133.77	13.577%	$151.932	$151.93	$151.95	$151.90
Purchase #2	$213.59	11.589%	$238.3429	$238.34	$238.35	$238.30
Purchase #3	$26.94	5.587%	$28.4451	$28.45	$28.45	$28.40
Purchase #4	$80.45	5.816%	$85.129	$85.13	$85.15	$85.10
Purchase #5	$212.66	10.275%	$234.5108	$234.51	$234.50	$234.50
Purchase #6	$165.91	10.186%	$182.8096	$182.81	$182.80	$182.80
Purchase #7	$50.92	3.757%	$52.8331	$52.83	$52.85	$52.80
7 purchase totals =	$884.24		$974.0025	$974.00	$974.05	$973.80