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	$210.32	5.835%	$222.5922	$222.59	$222.60	$222.60
Purchase #2	$139.75	11.848%	$156.3076	$156.31	$156.30	$156.30
Purchase #3	$155.61	11.134%	$172.9356	$172.94	$172.95	$172.90
Purchase #4	$166.58	12.713%	$187.7573	$187.76	$187.75	$187.80
Purchase #5	$28.96	4.709%	$30.3237	$30.32	$30.30	$30.30
Purchase #6	$183.57	3.643%	$190.2575	$190.26	$190.25	$190.30
Purchase #7	$120.27	11.612%	$134.2358	$134.24	$134.25	$134.20
7 purchase totals =	$1,005.06		$1,094.4097	$1,094.42	$1,094.40	$1,094.40