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	$114.78	7.345%	$123.2106	$123.21	$123.20	$123.20
Purchase #2	$99.76	7.195%	$106.9377	$106.94	$106.95	$106.90
Purchase #3	$221.78	7.324%	$238.0232	$238.02	$238.00	$238.00
Purchase #4	$56.59	5.305%	$59.5921	$59.59	$59.60	$59.60
Purchase #5	$203.69	8.267%	$220.5291	$220.53	$220.55	$220.50
Purchase #6	$133.61	10.585%	$147.7526	$147.75	$147.75	$147.80
Purchase #7	$237.34	11.500%	$264.6341	$264.63	$264.65	$264.60
7 purchase totals =	$1,067.55		$1,160.6794	$1,160.67	$1,160.70	$1,160.60