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	$118.80	7.653%	$127.8918	$127.89	$127.90	$127.90
Purchase #2	$133.34	9.318%	$145.7646	$145.76	$145.75	$145.80
Purchase #3	$103.46	13.736%	$117.6713	$117.67	$117.65	$117.70
Purchase #4	$142.57	5.741%	$150.7549	$150.75	$150.75	$150.80
Purchase #5	$66.82	4.155%	$69.5964	$69.60	$69.60	$69.60
Purchase #6	$76.66	11.372%	$85.3778	$85.38	$85.40	$85.40
Purchase #7	$93.91	5.757%	$99.3164	$99.32	$99.30	$99.30
7 purchase totals =	$735.56		$796.3732	$796.37	$796.35	$796.50