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	$195.86	13.616%	$222.5283	$222.53	$222.55	$222.50
Purchase #2	$178.48	5.480%	$188.2607	$188.26	$188.25	$188.30
Purchase #3	$67.72	3.588%	$70.1498	$70.15	$70.15	$70.10
Purchase #4	$212.28	3.348%	$219.3871	$219.39	$219.40	$219.40
Purchase #5	$199.63	11.116%	$221.8209	$221.82	$221.80	$221.80
Purchase #6	$166.46	7.728%	$179.324	$179.32	$179.30	$179.30
Purchase #7	$107.70	12.387%	$121.0408	$121.04	$121.05	$121.00
7 purchase totals =	$1,128.13		$1,222.5116	$1,222.51	$1,222.50	$1,222.40