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	$116.51	3.621%	$120.7288	$120.73	$120.75	$120.70
Purchase #2	$96.60	10.664%	$106.9014	$106.90	$106.90	$106.90
Purchase #3	$36.57	12.731%	$41.2257	$41.23	$41.25	$41.20
Purchase #4	$19.66	5.866%	$20.8133	$20.81	$20.80	$20.80
Purchase #5	$243.50	6.231%	$258.6725	$258.67	$258.65	$258.70
Purchase #6	$147.81	10.190%	$162.8718	$162.87	$162.85	$162.90
Purchase #7	$82.28	10.486%	$90.9079	$90.91	$90.90	$90.90
7 purchase totals =	$742.93		$802.1214	$802.12	$802.10	$802.10