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	$221.84	9.748%	$243.465	$243.47	$243.45	$243.50
Purchase #2	$11.96	12.208%	$13.4201	$13.42	$13.40	$13.40
Purchase #3	$250.47	8.851%	$272.6391	$272.64	$272.65	$272.60
Purchase #4	$6.35	4.107%	$6.6108	$6.61	$6.60	$6.60
Purchase #5	$116.26	6.481%	$123.7948	$123.79	$123.80	$123.80
Purchase #6	$92.43	13.478%	$104.8877	$104.89	$104.90	$104.90
Purchase #7	$232.33	11.865%	$259.896	$259.90	$259.90	$259.90
7 purchase totals =	$931.64		$1,024.7135	$1,024.72	$1,024.70	$1,024.70