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	$211.56	10.574%	$233.9304	$233.93	$233.95	$233.90
Purchase #2	$226.91	11.508%	$253.0228	$253.02	$253.00	$253.00
Purchase #3	$145.56	11.690%	$162.576	$162.58	$162.60	$162.60
Purchase #4	$100.53	12.769%	$113.3667	$113.37	$113.35	$113.40
Purchase #5	$156.45	13.527%	$177.613	$177.61	$177.60	$177.60
Purchase #6	$229.50	9.275%	$250.7861	$250.79	$250.80	$250.80
Purchase #7	$230.35	10.658%	$254.9007	$254.90	$254.90	$254.90
7 purchase totals =	$1,300.86		$1,446.1957	$1,446.20	$1,446.20	$1,446.20