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	$209.76	5.607%	$221.5212	$221.52	$221.50	$221.50
Purchase #2	$68.67	13.248%	$77.7674	$77.77	$77.75	$77.80
Purchase #3	$181.37	13.490%	$205.8368	$205.84	$205.85	$205.80
Purchase #4	$25.45	9.445%	$27.8538	$27.85	$27.85	$27.90
Purchase #5	$124.39	7.350%	$133.5327	$133.53	$133.55	$133.50
Purchase #6	$7.32	5.531%	$7.7249	$7.72	$7.70	$7.70
Purchase #7	$90.88	9.604%	$99.6081	$99.61	$99.60	$99.60
7 purchase totals =	$707.84		$773.8449	$773.84	$773.80	$773.80