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	$145.99	4.195%	$152.1143	$152.11	$152.10	$152.10
Purchase #2	$207.39	13.744%	$235.8937	$235.89	$235.90	$235.90
Purchase #3	$118.58	6.692%	$126.5154	$126.52	$126.50	$126.50
Purchase #4	$76.60	6.435%	$81.5292	$81.53	$81.55	$81.50
Purchase #5	$17.75	5.440%	$18.7156	$18.72	$18.70	$18.70
Purchase #6	$205.49	12.852%	$231.8996	$231.90	$231.90	$231.90
Purchase #7	$148.60	5.238%	$156.3837	$156.38	$156.40	$156.40
7 purchase totals =	$920.40		$1,003.0515	$1,003.05	$1,003.05	$1,003.00