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	$247.86	9.783%	$272.1081	$272.11	$272.10	$272.10
Purchase #2	$119.75	13.757%	$136.224	$136.22	$136.20	$136.20
Purchase #3	$225.89	4.788%	$236.7056	$236.71	$236.70	$236.70
Purchase #4	$180.44	6.143%	$191.5244	$191.52	$191.50	$191.50
Purchase #5	$229.61	6.764%	$245.1408	$245.14	$245.15	$245.10
Purchase #6	$174.28	4.501%	$182.1243	$182.12	$182.10	$182.10
Purchase #7	$72.89	13.542%	$82.7608	$82.76	$82.75	$82.80
7 purchase totals =	$1,250.72		$1,346.5880	$1,346.58	$1,346.50	$1,346.50