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	$188.67	13.497%	$214.1348	$214.13	$214.15	$214.10
Purchase #2	$245.75	11.696%	$274.4929	$274.49	$274.50	$274.50
Purchase #3	$48.40	13.275%	$54.8251	$54.83	$54.85	$54.80
Purchase #4	$156.56	12.200%	$175.6603	$175.66	$175.65	$175.70
Purchase #5	$125.88	12.253%	$141.3041	$141.30	$141.30	$141.30
Purchase #6	$163.72	12.540%	$184.2505	$184.25	$184.25	$184.30
Purchase #7	$151.35	13.722%	$172.1182	$172.12	$172.10	$172.10
7 purchase totals =	$1,080.33		$1,216.7859	$1,216.78	$1,216.80	$1,216.80