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	$206.57	7.732%	$222.542	$222.54	$222.55	$222.50
Purchase #2	$80.86	12.315%	$90.8179	$90.82	$90.80	$90.80
Purchase #3	$64.36	13.590%	$73.1065	$73.11	$73.10	$73.10
Purchase #4	$175.55	5.432%	$185.0859	$185.09	$185.10	$185.10
Purchase #5	$30.27	10.362%	$33.4066	$33.41	$33.40	$33.40
Purchase #6	$34.83	8.189%	$37.6822	$37.68	$37.70	$37.70
Purchase #7	$115.82	9.148%	$126.4152	$126.42	$126.40	$126.40
7 purchase totals =	$708.26		$769.0563	$769.07	$769.05	$769.00