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	$42.34	6.821%	$45.228	$45.23	$45.25	$45.20
Purchase #2	$179.45	8.495%	$194.6943	$194.69	$194.70	$194.70
Purchase #3	$50.27	8.458%	$54.5218	$54.52	$54.50	$54.50
Purchase #4	$95.33	10.818%	$105.6428	$105.64	$105.65	$105.60
Purchase #5	$186.73	6.651%	$199.1494	$199.15	$199.15	$199.10
Purchase #6	$148.85	11.732%	$166.3131	$166.31	$166.30	$166.30
Purchase #7	$77.69	4.783%	$81.4059	$81.41	$81.40	$81.40
7 purchase totals =	$780.66		$846.9553	$846.95	$846.95	$846.80