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	$199.38	3.810%	$206.9764	$206.98	$207.00	$207.00
Purchase #2	$105.72	10.303%	$116.6123	$116.61	$116.60	$116.60
Purchase #3	$89.26	4.237%	$93.0419	$93.04	$93.05	$93.00
Purchase #4	$227.30	6.375%	$241.7904	$241.79	$241.80	$241.80
Purchase #5	$105.61	10.135%	$116.3136	$116.31	$116.30	$116.30
Purchase #6	$143.72	5.229%	$151.2351	$151.24	$151.25	$151.20
Purchase #7	$108.82	13.542%	$123.5564	$123.56	$123.55	$123.60
7 purchase totals =	$979.81		$1,049.5261	$1,049.53	$1,049.55	$1,049.50