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	$63.61	3.409%	$65.7785	$65.78	$65.80	$65.80
Purchase #2	$17.44	4.332%	$18.1955	$18.20	$18.20	$18.20
Purchase #3	$109.59	13.833%	$124.7496	$124.75	$124.75	$124.70
Purchase #4	$177.42	4.473%	$185.356	$185.36	$185.35	$185.40
Purchase #5	$183.77	7.144%	$196.8985	$196.90	$196.90	$196.90
Purchase #6	$140.43	11.616%	$156.7423	$156.74	$156.75	$156.70
Purchase #7	$45.56	10.837%	$50.4973	$50.50	$50.50	$50.50
7 purchase totals =	$737.82		$798.2177	$798.23	$798.25	$798.20