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	$148.50	13.335%	$168.3025	$168.30	$168.30	$168.30
Purchase #2	$174.98	11.212%	$194.5988	$194.60	$194.60	$194.60
Purchase #3	$106.92	4.729%	$111.9762	$111.98	$112.00	$112.00
Purchase #4	$206.44	13.760%	$234.8461	$234.85	$234.85	$234.80
Purchase #5	$53.70	10.111%	$59.1296	$59.13	$59.15	$59.10
Purchase #6	$134.97	4.480%	$141.0167	$141.02	$141.00	$141.00
Purchase #7	$224.38	7.697%	$241.6505	$241.65	$241.65	$241.70
7 purchase totals =	$1,049.89		$1,151.5204	$1,151.53	$1,151.55	$1,151.50