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	$214.85	13.641%	$244.1577	$244.16	$244.15	$244.20
Purchase #2	$47.59	6.373%	$50.6229	$50.62	$50.60	$50.60
Purchase #3	$72.26	7.442%	$77.6376	$77.64	$77.65	$77.60
Purchase #4	$67.61	8.765%	$73.536	$73.54	$73.55	$73.50
Purchase #5	$93.55	7.851%	$100.8946	$100.89	$100.90	$100.90
Purchase #6	$80.51	11.629%	$89.8725	$89.87	$89.85	$89.90
Purchase #7	$54.32	13.874%	$61.8564	$61.86	$61.85	$61.90
7 purchase totals =	$630.69		$698.5777	$698.58	$698.55	$698.60