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	$129.27	9.605%	$141.6864	$141.69	$141.70	$141.70
Purchase #2	$133.47	5.507%	$140.8202	$140.82	$140.80	$140.80
Purchase #3	$185.90	10.142%	$204.754	$204.75	$204.75	$204.80
Purchase #4	$9.59	9.440%	$10.4953	$10.50	$10.50	$10.50
Purchase #5	$35.92	12.755%	$40.5016	$40.50	$40.50	$40.50
Purchase #6	$247.57	7.579%	$266.3333	$266.33	$266.35	$266.30
Purchase #7	$81.50	12.440%	$91.6386	$91.64	$91.65	$91.60
7 purchase totals =	$823.22		$896.2294	$896.23	$896.25	$896.20