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	$133.89	10.116%	$147.4343	$147.43	$147.45	$147.40
Purchase #2	$196.97	10.103%	$216.8699	$216.87	$216.85	$216.90
Purchase #3	$67.46	10.657%	$74.6492	$74.65	$74.65	$74.60
Purchase #4	$188.75	5.606%	$199.3313	$199.33	$199.35	$199.30
Purchase #5	$78.90	13.253%	$89.3566	$89.36	$89.35	$89.40
Purchase #6	$213.34	3.111%	$219.977	$219.98	$220.00	$220.00
Purchase #7	$64.49	4.696%	$67.5185	$67.52	$67.50	$67.50
7 purchase totals =	$943.80		$1,015.1368	$1,015.14	$1,015.15	$1,015.10