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	$40.56	11.308%	$45.1465	$45.15	$45.15	$45.10
Purchase #2	$64.32	5.287%	$67.7206	$67.72	$67.70	$67.70
Purchase #3	$94.50	10.345%	$104.276	$104.28	$104.30	$104.30
Purchase #4	$16.29	13.390%	$18.4712	$18.47	$18.45	$18.50
Purchase #5	$249.33	9.185%	$272.231	$272.23	$272.25	$272.20
Purchase #6	$186.97	3.356%	$193.2447	$193.24	$193.25	$193.20
Purchase #7	$37.31	7.363%	$40.0571	$40.06	$40.05	$40.10
7 purchase totals =	$689.28		$741.1471	$741.15	$741.15	$741.10