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	$86.90	10.664%	$96.167	$96.17	$96.15	$96.20
Purchase #2	$97.34	11.676%	$108.7054	$108.71	$108.70	$108.70
Purchase #3	$236.98	8.336%	$256.7347	$256.73	$256.75	$256.70
Purchase #4	$130.46	8.109%	$141.039	$141.04	$141.05	$141.00
Purchase #5	$72.25	10.514%	$79.8464	$79.85	$79.85	$79.80
Purchase #6	$18.82	4.618%	$19.6891	$19.69	$19.70	$19.70
Purchase #7	$95.45	4.113%	$99.3759	$99.38	$99.40	$99.40
7 purchase totals =	$738.20		$801.5575	$801.57	$801.60	$801.50