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	$105.62	7.601%	$113.6482	$113.65	$113.65	$113.60
Purchase #2	$33.86	10.490%	$37.4119	$37.41	$37.40	$37.40
Purchase #3	$245.46	11.382%	$273.3983	$273.40	$273.40	$273.40
Purchase #4	$50.92	7.737%	$54.8597	$54.86	$54.85	$54.90
Purchase #5	$76.31	9.476%	$83.5411	$83.54	$83.55	$83.50
Purchase #6	$88.54	4.301%	$92.3481	$92.35	$92.35	$92.30
Purchase #7	$172.32	12.302%	$193.5188	$193.52	$193.50	$193.50
7 purchase totals =	$773.03		$848.7261	$848.73	$848.70	$848.60