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	$56.60	12.237%	$63.5261	$63.53	$63.55	$63.50
Purchase #2	$201.54	4.132%	$209.8676	$209.87	$209.85	$209.90
Purchase #3	$211.32	11.482%	$235.5838	$235.58	$235.60	$235.60
Purchase #4	$218.51	13.326%	$247.6286	$247.63	$247.65	$247.60
Purchase #5	$198.36	11.585%	$221.34	$221.34	$221.35	$221.30
Purchase #6	$89.34	3.660%	$92.6098	$92.61	$92.60	$92.60
Purchase #7	$89.27	12.690%	$100.5984	$100.60	$100.60	$100.60
7 purchase totals =	$1,064.94		$1,171.1543	$1,171.16	$1,171.20	$1,171.10