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	$81.79	4.728%	$85.657	$85.66	$85.65	$85.70
Purchase #2	$173.86	11.624%	$194.0695	$194.07	$194.05	$194.10
Purchase #3	$234.37	13.736%	$266.5631	$266.56	$266.55	$266.60
Purchase #4	$43.37	4.141%	$45.166	$45.17	$45.15	$45.20
Purchase #5	$223.49	3.549%	$231.4217	$231.42	$231.40	$231.40
Purchase #6	$206.36	5.358%	$217.4168	$217.42	$217.40	$217.40
Purchase #7	$82.90	4.123%	$86.318	$86.32	$86.30	$86.30
7 purchase totals =	$1,046.14		$1,126.6121	$1,126.62	$1,126.50	$1,126.70