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	$51.57	8.170%	$55.7833	$55.78	$55.80	$55.80
Purchase #2	$50.60	10.166%	$55.744	$55.74	$55.75	$55.70
Purchase #3	$249.73	5.150%	$262.5911	$262.59	$262.60	$262.60
Purchase #4	$73.36	8.115%	$79.3132	$79.31	$79.30	$79.30
Purchase #5	$31.85	11.105%	$35.3869	$35.39	$35.40	$35.40
Purchase #6	$70.62	11.758%	$78.9235	$78.92	$78.90	$78.90
Purchase #7	$147.79	7.521%	$158.9053	$158.91	$158.90	$158.90
7 purchase totals =	$675.52		$726.6473	$726.64	$726.65	$726.60