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	$123.71	5.778%	$130.858	$130.86	$130.85	$130.90
Purchase #2	$136.59	6.556%	$145.5448	$145.54	$145.55	$145.50
Purchase #3	$89.72	7.444%	$96.3988	$96.40	$96.40	$96.40
Purchase #4	$238.99	12.747%	$269.4541	$269.45	$269.45	$269.50
Purchase #5	$28.96	3.749%	$30.0457	$30.05	$30.05	$30.00
Purchase #6	$61.82	4.488%	$64.5945	$64.59	$64.60	$64.60
Purchase #7	$191.46	13.806%	$217.893	$217.89	$217.90	$217.90
7 purchase totals =	$871.25		$954.7889	$954.78	$954.80	$954.80