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	$65.91	6.616%	$70.2706	$70.27	$70.25	$70.30
Purchase #2	$192.66	7.369%	$206.8571	$206.86	$206.85	$206.90
Purchase #3	$231.29	11.834%	$258.6609	$258.66	$258.65	$258.70
Purchase #4	$112.32	13.208%	$127.1552	$127.16	$127.15	$127.20
Purchase #5	$105.33	11.642%	$117.5925	$117.59	$117.60	$117.60
Purchase #6	$199.54	6.226%	$211.9634	$211.96	$211.95	$212.00
Purchase #7	$28.88	12.115%	$32.3788	$32.38	$32.40	$32.40
7 purchase totals =	$935.93		$1,024.8785	$1,024.88	$1,024.85	$1,025.10