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	$140.39	5.393%	$147.9612	$147.96	$147.95	$148.00
Purchase #2	$151.56	7.103%	$162.3253	$162.33	$162.35	$162.30
Purchase #3	$148.53	5.429%	$156.5937	$156.59	$156.60	$156.60
Purchase #4	$248.74	11.370%	$277.0217	$277.02	$277.00	$277.00
Purchase #5	$90.85	5.193%	$95.5678	$95.57	$95.55	$95.60
Purchase #6	$119.36	8.301%	$129.2681	$129.27	$129.25	$129.30
Purchase #7	$196.60	10.196%	$216.6453	$216.65	$216.65	$216.60
7 purchase totals =	$1,096.03		$1,185.3831	$1,185.39	$1,185.35	$1,185.40