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	$99.30	6.373%	$105.6284	$105.63	$105.65	$105.60
Purchase #2	$194.75	5.557%	$205.5723	$205.57	$205.55	$205.60
Purchase #3	$201.60	9.107%	$219.9597	$219.96	$219.95	$220.00
Purchase #4	$237.95	5.139%	$250.1783	$250.18	$250.20	$250.20
Purchase #5	$37.28	3.178%	$38.4648	$38.46	$38.45	$38.50
Purchase #6	$173.68	13.269%	$196.7256	$196.73	$196.75	$196.70
Purchase #7	$60.35	7.555%	$64.9094	$64.91	$64.90	$64.90
7 purchase totals =	$1,004.91		$1,081.4385	$1,081.44	$1,081.45	$1,081.50