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	$40.31	10.526%	$44.553	$44.55	$44.55	$44.60
Purchase #2	$83.84	8.455%	$90.9287	$90.93	$90.95	$90.90
Purchase #3	$169.57	6.438%	$180.4869	$180.49	$180.50	$180.50
Purchase #4	$49.26	13.377%	$55.8495	$55.85	$55.85	$55.80
Purchase #5	$97.79	13.619%	$111.108	$111.11	$111.10	$111.10
Purchase #6	$198.46	3.368%	$205.1441	$205.14	$205.15	$205.10
Purchase #7	$165.80	12.130%	$185.9115	$185.91	$185.90	$185.90
7 purchase totals =	$805.03		$873.9817	$873.98	$874.00	$873.90