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	$201.92	7.396%	$216.854	$216.85	$216.85	$216.90
Purchase #2	$144.89	3.618%	$150.1321	$150.13	$150.15	$150.10
Purchase #3	$200.60	4.530%	$209.6872	$209.69	$209.70	$209.70
Purchase #4	$63.94	13.472%	$72.554	$72.55	$72.55	$72.60
Purchase #5	$104.61	9.329%	$114.3691	$114.37	$114.35	$114.40
Purchase #6	$248.81	6.478%	$264.9279	$264.93	$264.95	$264.90
Purchase #7	$213.25	4.632%	$223.1277	$223.13	$223.15	$223.10
7 purchase totals =	$1,178.02		$1,251.6520	$1,251.65	$1,251.70	$1,251.70