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	$127.59	10.692%	$141.2319	$141.23	$141.25	$141.20
Purchase #2	$179.87	4.711%	$188.3437	$188.34	$188.35	$188.30
Purchase #3	$11.93	6.164%	$12.6654	$12.67	$12.65	$12.70
Purchase #4	$27.88	11.374%	$31.0511	$31.05	$31.05	$31.10
Purchase #5	$32.60	12.643%	$36.7216	$36.72	$36.70	$36.70
Purchase #6	$153.75	13.854%	$175.0505	$175.05	$175.05	$175.10
Purchase #7	$235.90	6.206%	$250.54	$250.54	$250.55	$250.50
7 purchase totals =	$769.52		$835.6042	$835.60	$835.60	$835.60