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	$43.54	13.529%	$49.4305	$49.43	$49.45	$49.40
Purchase #2	$79.66	6.708%	$85.0036	$85.00	$85.00	$85.00
Purchase #3	$89.97	4.600%	$94.1086	$94.11	$94.10	$94.10
Purchase #4	$86.61	8.601%	$94.0593	$94.06	$94.05	$94.10
Purchase #5	$136.65	11.134%	$151.8646	$151.86	$151.85	$151.90
Purchase #6	$74.78	5.252%	$78.7074	$78.71	$78.70	$78.70
Purchase #7	$43.77	13.797%	$49.8089	$49.81	$49.80	$49.80
7 purchase totals =	$554.98		$602.9829	$602.98	$602.95	$603.00