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	$90.62	13.532%	$102.8827	$102.88	$102.90	$102.90
Purchase #2	$148.67	4.189%	$154.8978	$154.90	$154.90	$154.90
Purchase #3	$170.77	13.473%	$193.7778	$193.78	$193.80	$193.80
Purchase #4	$59.85	10.672%	$66.2372	$66.24	$66.25	$66.20
Purchase #5	$248.33	13.846%	$282.7138	$282.71	$282.70	$282.70
Purchase #6	$38.98	9.471%	$42.6718	$42.67	$42.65	$42.70
Purchase #7	$165.45	13.823%	$188.3202	$188.32	$188.30	$188.30
7 purchase totals =	$922.67		$1,031.5013	$1,031.50	$1,031.50	$1,031.50