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	$69.56	4.763%	$72.8731	$72.87	$72.85	$72.90
Purchase #2	$191.66	12.815%	$216.2212	$216.22	$216.20	$216.20
Purchase #3	$183.90	12.751%	$207.3491	$207.35	$207.35	$207.30
Purchase #4	$168.49	13.371%	$191.0188	$191.02	$191.00	$191.00
Purchase #5	$196.83	12.808%	$222.04	$222.04	$222.05	$222.00
Purchase #6	$120.43	11.643%	$134.4517	$134.45	$134.45	$134.50
Purchase #7	$173.42	3.795%	$180.0013	$180.00	$180.00	$180.00
7 purchase totals =	$1,104.29		$1,223.9552	$1,223.95	$1,223.90	$1,223.90