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	$140.58	7.853%	$151.6197	$151.62	$151.60	$151.60
Purchase #2	$171.68	11.509%	$191.4387	$191.44	$191.45	$191.40
Purchase #3	$185.37	13.220%	$209.8759	$209.88	$209.90	$209.90
Purchase #4	$28.79	12.489%	$32.3856	$32.39	$32.40	$32.40
Purchase #5	$131.36	11.505%	$146.473	$146.47	$146.45	$146.50
Purchase #6	$54.26	10.608%	$60.0159	$60.02	$60.00	$60.00
Purchase #7	$194.83	12.341%	$218.874	$218.87	$218.85	$218.90
7 purchase totals =	$906.87		$1,010.6828	$1,010.69	$1,010.65	$1,010.70