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	$186.26	10.783%	$206.3444	$206.34	$206.35	$206.30
Purchase #2	$250.73	13.433%	$284.4106	$284.41	$284.40	$284.40
Purchase #3	$140.26	5.679%	$148.2254	$148.23	$148.25	$148.20
Purchase #4	$43.86	10.118%	$48.2978	$48.30	$48.30	$48.30
Purchase #5	$55.90	10.492%	$61.765	$61.77	$61.75	$61.80
Purchase #6	$72.73	13.362%	$82.4482	$82.45	$82.45	$82.40
Purchase #7	$166.65	8.587%	$180.9602	$180.96	$180.95	$181.00
7 purchase totals =	$916.39		$1,012.4516	$1,012.46	$1,012.45	$1,012.40