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	$235.86	9.517%	$258.3068	$258.31	$258.30	$258.30
Purchase #2	$142.43	9.801%	$156.3896	$156.39	$156.40	$156.40
Purchase #3	$10.29	7.492%	$11.0609	$11.06	$11.05	$11.10
Purchase #4	$118.32	4.413%	$123.5415	$123.54	$123.55	$123.50
Purchase #5	$70.79	4.580%	$74.0322	$74.03	$74.05	$74.00
Purchase #6	$21.54	5.635%	$22.7538	$22.75	$22.75	$22.80
Purchase #7	$136.50	7.274%	$146.429	$146.43	$146.45	$146.40
7 purchase totals =	$735.73		$792.5138	$792.51	$792.55	$792.50