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	$66.88	8.502%	$72.5661	$72.57	$72.55	$72.60
Purchase #2	$235.46	5.226%	$247.7651	$247.77	$247.75	$247.80
Purchase #3	$143.60	4.104%	$149.4933	$149.49	$149.50	$149.50
Purchase #4	$82.57	8.247%	$89.3795	$89.38	$89.40	$89.40
Purchase #5	$131.29	6.311%	$139.5757	$139.58	$139.60	$139.60
Purchase #6	$227.77	8.497%	$247.1236	$247.12	$247.10	$247.10
Purchase #7	$137.27	8.159%	$148.4699	$148.47	$148.45	$148.50
7 purchase totals =	$1,024.84		$1,094.3732	$1,094.38	$1,094.35	$1,094.50