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	$40.84	10.253%	$45.0273	$45.03	$45.05	$45.00
Purchase #2	$89.79	11.795%	$100.3807	$100.38	$100.40	$100.40
Purchase #3	$233.78	6.672%	$249.3778	$249.38	$249.40	$249.40
Purchase #4	$44.50	13.621%	$50.5613	$50.56	$50.55	$50.60
Purchase #5	$219.95	7.642%	$236.7586	$236.76	$236.75	$236.80
Purchase #6	$27.57	6.653%	$29.4042	$29.40	$29.40	$29.40
Purchase #7	$226.36	12.596%	$254.8723	$254.87	$254.85	$254.90
7 purchase totals =	$882.79		$966.3822	$966.38	$966.40	$966.50