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	$9.83	9.172%	$10.7316	$10.73	$10.75	$10.70
Purchase #2	$42.73	3.490%	$44.2213	$44.22	$44.20	$44.20
Purchase #3	$81.38	9.516%	$89.1241	$89.12	$89.10	$89.10
Purchase #4	$79.50	13.627%	$90.3335	$90.33	$90.35	$90.30
Purchase #5	$151.52	5.785%	$160.2854	$160.29	$160.30	$160.30
Purchase #6	$54.81	11.786%	$61.2699	$61.27	$61.25	$61.30
Purchase #7	$249.74	4.180%	$260.1791	$260.18	$260.20	$260.20
7 purchase totals =	$669.51		$716.1449	$716.14	$716.15	$716.10