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	$105.98	4.608%	$110.8636	$110.86	$110.85	$110.90
Purchase #2	$35.81	12.727%	$40.3675	$40.37	$40.35	$40.40
Purchase #3	$141.47	7.231%	$151.6997	$151.70	$151.70	$151.70
Purchase #4	$12.52	10.805%	$13.8728	$13.87	$13.85	$13.90
Purchase #5	$145.52	7.609%	$156.5926	$156.59	$156.60	$156.60
Purchase #6	$58.59	4.826%	$61.4176	$61.42	$61.40	$61.40
Purchase #7	$234.61	11.686%	$262.0265	$262.03	$262.05	$262.00
7 purchase totals =	$734.50		$796.8403	$796.84	$796.80	$796.90