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	$66.49	8.252%	$71.9768	$71.98	$72.00	$72.00
Purchase #2	$149.72	11.783%	$167.3615	$167.36	$167.35	$167.40
Purchase #3	$12.58	12.118%	$14.1044	$14.10	$14.10	$14.10
Purchase #4	$238.78	3.557%	$247.2734	$247.27	$247.25	$247.30
Purchase #5	$142.71	5.730%	$150.8873	$150.89	$150.90	$150.90
Purchase #6	$61.43	7.157%	$65.8265	$65.83	$65.85	$65.80
Purchase #7	$232.49	4.286%	$242.4545	$242.45	$242.45	$242.50
7 purchase totals =	$904.20		$959.8844	$959.88	$959.90	$960.00