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	$197.56	3.606%	$204.684	$204.68	$204.70	$204.70
Purchase #2	$225.45	8.348%	$244.2706	$244.27	$244.25	$244.30
Purchase #3	$162.38	4.424%	$169.5637	$169.56	$169.55	$169.60
Purchase #4	$182.42	8.439%	$197.8144	$197.81	$197.80	$197.80
Purchase #5	$83.72	6.853%	$89.4573	$89.46	$89.45	$89.50
Purchase #6	$54.71	3.189%	$56.4547	$56.45	$56.45	$56.50
Purchase #7	$50.52	10.131%	$55.6382	$55.64	$55.65	$55.60
7 purchase totals =	$956.76		$1,017.8829	$1,017.87	$1,017.85	$1,018.00