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	$41.82	12.746%	$47.1504	$47.15	$47.15	$47.20
Purchase #2	$42.71	7.482%	$45.9056	$45.91	$45.90	$45.90
Purchase #3	$85.28	7.656%	$91.809	$91.81	$91.80	$91.80
Purchase #4	$151.53	12.357%	$170.2546	$170.25	$170.25	$170.30
Purchase #5	$205.93	12.588%	$231.8525	$231.85	$231.85	$231.90
Purchase #6	$236.34	11.718%	$264.0343	$264.03	$264.05	$264.00
Purchase #7	$61.86	6.186%	$65.6867	$65.69	$65.70	$65.70
7 purchase totals =	$825.47		$916.6931	$916.69	$916.70	$916.80