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	$198.57	7.450%	$213.3635	$213.36	$213.35	$213.40
Purchase #2	$209.83	13.155%	$237.4331	$237.43	$237.45	$237.40
Purchase #3	$80.42	11.461%	$89.6369	$89.64	$89.65	$89.60
Purchase #4	$203.64	8.498%	$220.9453	$220.95	$220.95	$220.90
Purchase #5	$116.86	12.679%	$131.6767	$131.68	$131.70	$131.70
Purchase #6	$64.61	8.373%	$70.0198	$70.02	$70.00	$70.00
Purchase #7	$172.60	4.639%	$180.6069	$180.61	$180.60	$180.60
7 purchase totals =	$1,046.53		$1,143.6822	$1,143.69	$1,143.70	$1,143.60