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	$142.63	6.474%	$151.8639	$151.86	$151.85	$151.90
Purchase #2	$228.47	7.370%	$245.3082	$245.31	$245.30	$245.30
Purchase #3	$33.66	3.364%	$34.7923	$34.79	$34.80	$34.80
Purchase #4	$250.31	12.319%	$281.1457	$281.15	$281.15	$281.10
Purchase #5	$104.97	5.849%	$111.1097	$111.11	$111.10	$111.10
Purchase #6	$22.32	5.320%	$23.5074	$23.51	$23.50	$23.50
Purchase #7	$29.57	13.649%	$33.606	$33.61	$33.60	$33.60
7 purchase totals =	$811.93		$881.3332	$881.34	$881.30	$881.30