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	$227.95	7.566%	$245.1967	$245.20	$245.20	$245.20
Purchase #2	$183.73	4.170%	$191.3915	$191.39	$191.40	$191.40
Purchase #3	$170.44	12.586%	$191.8916	$191.89	$191.90	$191.90
Purchase #4	$102.78	11.462%	$114.5606	$114.56	$114.55	$114.60
Purchase #5	$130.76	13.413%	$148.2988	$148.30	$148.30	$148.30
Purchase #6	$15.41	13.120%	$17.4318	$17.43	$17.45	$17.40
Purchase #7	$216.55	10.126%	$238.4779	$238.48	$238.50	$238.50
7 purchase totals =	$1,047.62		$1,147.2489	$1,147.25	$1,147.30	$1,147.30