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	$95.65	12.434%	$107.5431	$107.54	$107.55	$107.50
Purchase #2	$212.59	3.259%	$219.5183	$219.52	$219.50	$219.50
Purchase #3	$76.33	5.612%	$80.6136	$80.61	$80.60	$80.60
Purchase #4	$114.92	7.859%	$123.9516	$123.95	$123.95	$124.00
Purchase #5	$94.44	4.863%	$99.0326	$99.03	$99.05	$99.00
Purchase #6	$53.57	10.145%	$59.0047	$59.00	$59.00	$59.00
Purchase #7	$152.65	6.603%	$162.7295	$162.73	$162.75	$162.70
7 purchase totals =	$800.15		$852.3934	$852.38	$852.40	$852.30