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	$146.71	4.506%	$153.3208	$153.32	$153.30	$153.30
Purchase #2	$244.38	11.770%	$273.1435	$273.14	$273.15	$273.10
Purchase #3	$29.63	9.729%	$32.5127	$32.51	$32.50	$32.50
Purchase #4	$104.89	11.484%	$116.9356	$116.94	$116.95	$116.90
Purchase #5	$200.55	3.143%	$206.8533	$206.85	$206.85	$206.90
Purchase #6	$187.86	4.363%	$196.0563	$196.06	$196.05	$196.10
Purchase #7	$225.94	5.223%	$237.7408	$237.74	$237.75	$237.70
7 purchase totals =	$1,139.96		$1,216.5630	$1,216.56	$1,216.55	$1,216.50