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	$227.53	7.457%	$244.4969	$244.50	$244.50	$244.50
Purchase #2	$250.98	3.712%	$260.2964	$260.30	$260.30	$260.30
Purchase #3	$45.47	10.218%	$50.1161	$50.12	$50.10	$50.10
Purchase #4	$48.52	4.139%	$50.5282	$50.53	$50.55	$50.50
Purchase #5	$46.52	10.126%	$51.2306	$51.23	$51.25	$51.20
Purchase #6	$108.88	13.366%	$123.4329	$123.43	$123.45	$123.40
Purchase #7	$225.63	13.180%	$255.368	$255.37	$255.35	$255.40
7 purchase totals =	$953.53		$1,035.4691	$1,035.48	$1,035.50	$1,035.40