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	$232.31	5.791%	$245.7631	$245.76	$245.75	$245.80
Purchase #2	$109.58	7.399%	$117.6878	$117.69	$117.70	$117.70
Purchase #3	$197.86	5.622%	$208.9837	$208.98	$209.00	$209.00
Purchase #4	$153.88	8.117%	$166.3704	$166.37	$166.35	$166.40
Purchase #5	$69.69	5.498%	$73.5216	$73.52	$73.50	$73.50
Purchase #6	$78.28	13.556%	$88.8916	$88.89	$88.90	$88.90
Purchase #7	$147.67	8.674%	$160.4789	$160.48	$160.50	$160.50
7 purchase totals =	$989.27		$1,061.6971	$1,061.69	$1,061.70	$1,061.80