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	$137.93	12.184%	$154.7354	$154.74	$154.75	$154.70
Purchase #2	$229.50	12.679%	$258.5983	$258.60	$258.60	$258.60
Purchase #3	$7.30	6.422%	$7.7688	$7.77	$7.75	$7.80
Purchase #4	$166.89	4.771%	$174.8523	$174.85	$174.85	$174.90
Purchase #5	$168.90	11.580%	$188.4586	$188.46	$188.45	$188.50
Purchase #6	$174.70	9.632%	$191.5271	$191.53	$191.55	$191.50
Purchase #7	$54.39	7.472%	$58.454	$58.45	$58.45	$58.50
7 purchase totals =	$939.61		$1,034.3945	$1,034.40	$1,034.40	$1,034.50