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	$215.89	11.434%	$240.5749	$240.57	$240.55	$240.60
Purchase #2	$133.79	6.770%	$142.8476	$142.85	$142.85	$142.80
Purchase #3	$21.36	6.215%	$22.6875	$22.69	$22.70	$22.70
Purchase #4	$54.83	8.530%	$59.507	$59.51	$59.50	$59.50
Purchase #5	$231.41	8.429%	$250.9155	$250.92	$250.90	$250.90
Purchase #6	$221.60	9.194%	$241.9739	$241.97	$241.95	$242.00
Purchase #7	$81.29	6.580%	$86.6389	$86.64	$86.65	$86.60
7 purchase totals =	$960.17		$1,045.1453	$1,045.15	$1,045.10	$1,045.10