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	$130.79	7.851%	$141.0583	$141.06	$141.05	$141.10
Purchase #2	$119.87	7.238%	$128.5462	$128.55	$128.55	$128.50
Purchase #3	$174.40	5.309%	$183.6589	$183.66	$183.65	$183.70
Purchase #4	$131.34	4.351%	$137.0546	$137.05	$137.05	$137.10
Purchase #5	$56.95	4.747%	$59.6534	$59.65	$59.65	$59.70
Purchase #6	$155.82	11.383%	$173.557	$173.56	$173.55	$173.60
Purchase #7	$131.65	12.527%	$148.1418	$148.14	$148.15	$148.10
7 purchase totals =	$900.82		$971.6702	$971.67	$971.65	$971.80