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	$183.33	9.211%	$200.2165	$200.22	$200.20	$200.20
Purchase #2	$227.89	4.530%	$238.2134	$238.21	$238.20	$238.20
Purchase #3	$29.78	11.582%	$33.2291	$33.23	$33.25	$33.20
Purchase #4	$206.83	8.149%	$223.6846	$223.68	$223.70	$223.70
Purchase #5	$179.94	3.809%	$186.7939	$186.79	$186.80	$186.80
Purchase #6	$33.70	7.371%	$36.184	$36.18	$36.20	$36.20
Purchase #7	$73.70	13.248%	$83.4638	$83.46	$83.45	$83.50
7 purchase totals =	$935.17		$1,001.7853	$1,001.77	$1,001.80	$1,001.80