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	$114.60	11.787%	$128.1079	$128.11	$128.10	$128.10
Purchase #2	$236.77	7.495%	$254.5159	$254.52	$254.50	$254.50
Purchase #3	$217.94	10.385%	$240.5731	$240.57	$240.55	$240.60
Purchase #4	$95.25	8.662%	$103.5006	$103.50	$103.50	$103.50
Purchase #5	$27.55	8.364%	$29.8543	$29.85	$29.85	$29.90
Purchase #6	$241.68	13.829%	$275.1019	$275.10	$275.10	$275.10
Purchase #7	$37.63	13.736%	$42.7989	$42.80	$42.80	$42.80
7 purchase totals =	$971.42		$1,074.4526	$1,074.45	$1,074.40	$1,074.50