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	$63.70	13.196%	$72.1059	$72.11	$72.10	$72.10
Purchase #2	$38.91	7.809%	$41.9485	$41.95	$41.95	$41.90
Purchase #3	$96.47	4.511%	$100.8218	$100.82	$100.80	$100.80
Purchase #4	$104.81	11.568%	$116.9344	$116.93	$116.95	$116.90
Purchase #5	$78.32	3.836%	$81.3244	$81.32	$81.30	$81.30
Purchase #6	$47.60	9.482%	$52.1134	$52.11	$52.10	$52.10
Purchase #7	$34.67	10.793%	$38.4119	$38.41	$38.40	$38.40
7 purchase totals =	$464.48		$503.6603	$503.65	$503.60	$503.50