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	$185.25	3.406%	$191.5596	$191.56	$191.55	$191.60
Purchase #2	$156.41	4.117%	$162.8494	$162.85	$162.85	$162.80
Purchase #3	$134.63	13.706%	$153.0824	$153.08	$153.10	$153.10
Purchase #4	$194.89	11.289%	$216.8911	$216.89	$216.90	$216.90
Purchase #5	$149.87	5.711%	$158.4291	$158.43	$158.45	$158.40
Purchase #6	$37.78	4.435%	$39.4555	$39.46	$39.45	$39.50
Purchase #7	$22.43	4.800%	$23.5066	$23.51	$23.50	$23.50
7 purchase totals =	$881.26		$945.7737	$945.78	$945.80	$945.80