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	$93.94	11.265%	$104.5223	$104.52	$104.50	$104.50
Purchase #2	$226.98	11.667%	$253.4618	$253.46	$253.45	$253.50
Purchase #3	$68.86	11.826%	$77.0034	$77.00	$77.00	$77.00
Purchase #4	$109.97	4.407%	$114.8164	$114.82	$114.80	$114.80
Purchase #5	$60.68	4.860%	$63.629	$63.63	$63.65	$63.60
Purchase #6	$93.33	13.396%	$105.8325	$105.83	$105.85	$105.80
Purchase #7	$148.39	13.824%	$168.9034	$168.90	$168.90	$168.90
7 purchase totals =	$802.15		$888.1688	$888.16	$888.15	$888.10