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	$42.75	8.444%	$46.3598	$46.36	$46.35	$46.40
Purchase #2	$219.89	7.121%	$235.5484	$235.55	$235.55	$235.50
Purchase #3	$102.59	8.854%	$111.6733	$111.67	$111.65	$111.70
Purchase #4	$158.55	5.843%	$167.8141	$167.81	$167.80	$167.80
Purchase #5	$180.82	5.279%	$190.3655	$190.37	$190.35	$190.40
Purchase #6	$96.88	5.797%	$102.4961	$102.50	$102.50	$102.50
Purchase #7	$106.32	7.618%	$114.4195	$114.42	$114.40	$114.40
7 purchase totals =	$907.80		$968.6767	$968.68	$968.60	$968.70