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	$30.88	8.505%	$33.5063	$33.51	$33.50	$33.50
Purchase #2	$161.36	11.135%	$179.3274	$179.33	$179.35	$179.30
Purchase #3	$191.34	11.406%	$213.1642	$213.16	$213.15	$213.20
Purchase #4	$39.93	6.610%	$42.5694	$42.57	$42.55	$42.60
Purchase #5	$127.52	3.456%	$131.9271	$131.93	$131.95	$131.90
Purchase #6	$173.37	6.656%	$184.9095	$184.91	$184.90	$184.90
Purchase #7	$204.53	5.250%	$215.2678	$215.27	$215.25	$215.30
7 purchase totals =	$928.93		$1,000.6717	$1,000.68	$1,000.65	$1,000.70