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	$117.64	13.609%	$133.6496	$133.65	$133.65	$133.60
Purchase #2	$214.54	6.436%	$228.3478	$228.35	$228.35	$228.30
Purchase #3	$217.37	3.590%	$225.1736	$225.17	$225.15	$225.20
Purchase #4	$97.71	11.704%	$109.146	$109.15	$109.15	$109.10
Purchase #5	$88.52	3.611%	$91.7165	$91.72	$91.70	$91.70
Purchase #6	$198.27	4.350%	$206.8947	$206.89	$206.90	$206.90
Purchase #7	$64.78	13.523%	$73.5402	$73.54	$73.55	$73.50
7 purchase totals =	$998.83		$1,068.4684	$1,068.47	$1,068.45	$1,068.30