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	$70.55	9.365%	$77.157	$77.16	$77.15	$77.20
Purchase #2	$130.67	10.663%	$144.6033	$144.60	$144.60	$144.60
Purchase #3	$45.63	9.833%	$50.1168	$50.12	$50.10	$50.10
Purchase #4	$134.25	12.362%	$150.846	$150.85	$150.85	$150.80
Purchase #5	$175.43	7.626%	$188.8083	$188.81	$188.80	$188.80
Purchase #6	$219.25	3.761%	$227.496	$227.50	$227.50	$227.50
Purchase #7	$243.80	6.332%	$259.2374	$259.24	$259.25	$259.20
7 purchase totals =	$1,019.58		$1,098.2648	$1,098.28	$1,098.25	$1,098.20