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	$179.42	4.227%	$187.0041	$187.00	$187.00	$187.00
Purchase #2	$89.70	5.795%	$94.8981	$94.90	$94.90	$94.90
Purchase #3	$174.50	9.138%	$190.4458	$190.45	$190.45	$190.40
Purchase #4	$129.94	7.209%	$139.3074	$139.31	$139.30	$139.30
Purchase #5	$85.51	3.227%	$88.2694	$88.27	$88.25	$88.30
Purchase #6	$156.52	7.448%	$168.1776	$168.18	$168.20	$168.20
Purchase #7	$171.69	12.548%	$193.2337	$193.23	$193.25	$193.20
7 purchase totals =	$987.28		$1,061.3361	$1,061.34	$1,061.35	$1,061.30