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	$189.77	10.131%	$208.9956	$209.00	$209.00	$209.00
Purchase #2	$105.51	11.383%	$117.5202	$117.52	$117.50	$117.50
Purchase #3	$43.96	4.277%	$45.8402	$45.84	$45.85	$45.80
Purchase #4	$33.40	12.721%	$37.6488	$37.65	$37.65	$37.60
Purchase #5	$169.66	3.248%	$175.1706	$175.17	$175.15	$175.20
Purchase #6	$10.74	12.308%	$12.0619	$12.06	$12.05	$12.10
Purchase #7	$136.66	11.320%	$152.1299	$152.13	$152.15	$152.10
7 purchase totals =	$689.70		$749.3672	$749.37	$749.35	$749.30