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	$154.40	4.264%	$160.9836	$160.98	$161.00	$161.00
Purchase #2	$139.89	11.110%	$155.4318	$155.43	$155.45	$155.40
Purchase #3	$179.96	3.529%	$186.3108	$186.31	$186.30	$186.30
Purchase #4	$197.47	5.726%	$208.7771	$208.78	$208.80	$208.80
Purchase #5	$162.75	5.168%	$171.1609	$171.16	$171.15	$171.20
Purchase #6	$136.65	10.856%	$151.4847	$151.48	$151.50	$151.50
Purchase #7	$209.71	5.245%	$220.7093	$220.71	$220.70	$220.70
7 purchase totals =	$1,180.83		$1,254.8582	$1,254.85	$1,254.90	$1,254.90