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	$101.82	4.437%	$106.3378	$106.34	$106.35	$106.30
Purchase #2	$53.58	4.331%	$55.9005	$55.90	$55.90	$55.90
Purchase #3	$107.58	8.796%	$117.0427	$117.04	$117.05	$117.00
Purchase #4	$149.87	11.771%	$167.5112	$167.51	$167.50	$167.50
Purchase #5	$141.54	11.827%	$158.2799	$158.28	$158.30	$158.30
Purchase #6	$79.90	13.280%	$90.5107	$90.51	$90.50	$90.50
Purchase #7	$30.69	4.236%	$31.99	$31.99	$32.00	$32.00
7 purchase totals =	$664.98		$727.5728	$727.57	$727.60	$727.50