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	$155.83	11.731%	$174.1104	$174.11	$174.10	$174.10
Purchase #2	$173.95	12.409%	$195.5355	$195.54	$195.55	$195.50
Purchase #3	$144.74	9.714%	$158.8	$158.80	$158.80	$158.80
Purchase #4	$224.72	9.239%	$245.4819	$245.48	$245.50	$245.50
Purchase #5	$171.70	10.381%	$189.5242	$189.52	$189.50	$189.50
Purchase #6	$109.50	8.766%	$119.0988	$119.10	$119.10	$119.10
Purchase #7	$160.28	7.521%	$172.3347	$172.33	$172.35	$172.30
7 purchase totals =	$1,140.72		$1,254.8855	$1,254.88	$1,254.90	$1,254.80