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	$53.46	11.665%	$59.6961	$59.70	$59.70	$59.70
Purchase #2	$103.73	12.102%	$116.2834	$116.28	$116.30	$116.30
Purchase #3	$43.73	5.675%	$46.2117	$46.21	$46.20	$46.20
Purchase #4	$147.91	13.137%	$167.3409	$167.34	$167.35	$167.30
Purchase #5	$50.53	5.671%	$53.3956	$53.40	$53.40	$53.40
Purchase #6	$211.98	13.852%	$241.3435	$241.34	$241.35	$241.30
Purchase #7	$83.40	10.442%	$92.1086	$92.11	$92.10	$92.10
7 purchase totals =	$694.74		$776.3798	$776.38	$776.40	$776.30