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	$154.37	3.216%	$159.3345	$159.33	$159.35	$159.30
Purchase #2	$183.67	3.772%	$190.598	$190.60	$190.60	$190.60
Purchase #3	$162.47	10.784%	$179.9908	$179.99	$180.00	$180.00
Purchase #4	$36.53	11.480%	$40.7236	$40.72	$40.70	$40.70
Purchase #5	$157.34	13.158%	$178.0428	$178.04	$178.05	$178.00
Purchase #6	$232.38	8.157%	$251.3352	$251.34	$251.35	$251.30
Purchase #7	$117.40	11.659%	$131.0877	$131.09	$131.10	$131.10
7 purchase totals =	$1,044.16		$1,131.1126	$1,131.11	$1,131.15	$1,131.00