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	$195.74	10.664%	$216.6137	$216.61	$216.60	$216.60
Purchase #2	$26.68	3.239%	$27.5442	$27.54	$27.55	$27.50
Purchase #3	$40.88	3.533%	$42.3243	$42.32	$42.30	$42.30
Purchase #4	$35.97	7.705%	$38.7415	$38.74	$38.75	$38.70
Purchase #5	$9.60	11.740%	$10.727	$10.73	$10.75	$10.70
Purchase #6	$82.42	3.407%	$85.228	$85.23	$85.25	$85.20
Purchase #7	$100.27	6.324%	$106.6111	$106.61	$106.60	$106.60
7 purchase totals =	$491.56		$527.7898	$527.78	$527.80	$527.60