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	$203.43	10.757%	$225.313	$225.31	$225.30	$225.30
Purchase #2	$28.67	4.248%	$29.8879	$29.89	$29.90	$29.90
Purchase #3	$189.26	12.767%	$213.4228	$213.42	$213.40	$213.40
Purchase #4	$212.36	7.612%	$228.5248	$228.52	$228.50	$228.50
Purchase #5	$33.85	10.565%	$37.4263	$37.43	$37.45	$37.40
Purchase #6	$145.30	9.657%	$159.3316	$159.33	$159.35	$159.30
Purchase #7	$114.64	4.218%	$119.4755	$119.48	$119.50	$119.50
7 purchase totals =	$927.51		$1,013.3819	$1,013.38	$1,013.40	$1,013.30