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	$224.54	4.169%	$233.9011	$233.90	$233.90	$233.90
Purchase #2	$181.35	5.399%	$191.1411	$191.14	$191.15	$191.10
Purchase #3	$177.96	8.859%	$193.7255	$193.73	$193.75	$193.70
Purchase #4	$44.90	11.363%	$50.002	$50.00	$50.00	$50.00
Purchase #5	$167.79	11.386%	$186.8946	$186.89	$186.90	$186.90
Purchase #6	$151.90	13.377%	$172.2197	$172.22	$172.20	$172.20
Purchase #7	$85.67	12.321%	$96.2254	$96.23	$96.25	$96.20
7 purchase totals =	$1,034.11		$1,124.1094	$1,124.11	$1,124.15	$1,124.00