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	$145.39	4.315%	$151.6636	$151.66	$151.65	$151.70
Purchase #2	$61.26	11.549%	$68.3349	$68.33	$68.35	$68.30
Purchase #3	$249.70	12.868%	$281.8314	$281.83	$281.85	$281.80
Purchase #4	$49.59	12.288%	$55.6836	$55.68	$55.70	$55.70
Purchase #5	$163.78	13.713%	$186.2392	$186.24	$186.25	$186.20
Purchase #6	$88.66	12.143%	$99.426	$99.43	$99.45	$99.40
Purchase #7	$137.63	13.650%	$156.4165	$156.42	$156.40	$156.40
7 purchase totals =	$896.01		$999.5952	$999.59	$999.65	$999.50