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	$154.52	12.300%	$173.526	$173.53	$173.55	$173.50
Purchase #2	$232.43	11.435%	$259.0084	$259.01	$259.00	$259.00
Purchase #3	$130.46	12.244%	$146.4335	$146.43	$146.45	$146.40
Purchase #4	$245.56	6.831%	$262.3342	$262.33	$262.35	$262.30
Purchase #5	$230.28	11.131%	$255.9125	$255.91	$255.90	$255.90
Purchase #6	$155.92	12.411%	$175.2712	$175.27	$175.25	$175.30
Purchase #7	$240.85	9.148%	$262.883	$262.88	$262.90	$262.90
7 purchase totals =	$1,390.02		$1,535.3688	$1,535.36	$1,535.40	$1,535.30