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	$163.70	4.802%	$171.5609	$171.56	$171.55	$171.60
Purchase #2	$223.59	9.609%	$245.0748	$245.07	$245.05	$245.10
Purchase #3	$250.95	12.707%	$282.8382	$282.84	$282.85	$282.80
Purchase #4	$153.48	3.545%	$158.9209	$158.92	$158.90	$158.90
Purchase #5	$206.46	8.694%	$224.4096	$224.41	$224.40	$224.40
Purchase #6	$91.66	4.132%	$95.4474	$95.45	$95.45	$95.40
Purchase #7	$239.59	10.588%	$264.9578	$264.96	$264.95	$265.00
7 purchase totals =	$1,329.43		$1,443.2096	$1,443.21	$1,443.15	$1,443.20