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	$112.74	3.694%	$116.9046	$116.90	$116.90	$116.90
Purchase #2	$33.59	5.618%	$35.4771	$35.48	$35.50	$35.50
Purchase #3	$136.31	8.296%	$147.6183	$147.62	$147.60	$147.60
Purchase #4	$135.45	12.173%	$151.9383	$151.94	$151.95	$151.90
Purchase #5	$166.51	5.341%	$175.4033	$175.40	$175.40	$175.40
Purchase #6	$32.33	6.412%	$34.403	$34.40	$34.40	$34.40
Purchase #7	$210.58	6.261%	$223.7644	$223.76	$223.75	$223.80
7 purchase totals =	$827.51		$885.5090	$885.50	$885.50	$885.50