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	$160.64	4.547%	$167.9443	$167.94	$167.95	$167.90
Purchase #2	$71.81	5.637%	$75.8579	$75.86	$75.85	$75.90
Purchase #3	$14.61	3.546%	$15.1281	$15.13	$15.15	$15.10
Purchase #4	$228.50	6.338%	$242.9823	$242.98	$243.00	$243.00
Purchase #5	$86.73	3.215%	$89.5184	$89.52	$89.50	$89.50
Purchase #6	$226.78	4.110%	$236.1007	$236.10	$236.10	$236.10
Purchase #7	$101.55	9.791%	$111.4928	$111.49	$111.50	$111.50
7 purchase totals =	$890.62		$939.0245	$939.02	$939.05	$939.00