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	$142.41	10.263%	$157.0255	$157.03	$157.05	$157.00
Purchase #2	$100.35	10.848%	$111.236	$111.24	$111.25	$111.20
Purchase #3	$140.51	10.263%	$154.9305	$154.93	$154.95	$154.90
Purchase #4	$239.87	4.161%	$249.851	$249.85	$249.85	$249.90
Purchase #5	$190.46	10.515%	$210.4869	$210.49	$210.50	$210.50
Purchase #6	$93.83	12.821%	$105.8599	$105.86	$105.85	$105.90
Purchase #7	$235.44	3.868%	$244.5468	$244.55	$244.55	$244.50
7 purchase totals =	$1,142.87		$1,233.9366	$1,233.95	$1,234.00	$1,233.90