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	$61.41	9.110%	$67.0045	$67.00	$67.00	$67.00
Purchase #2	$109.50	7.627%	$117.8516	$117.85	$117.85	$117.90
Purchase #3	$37.37	9.133%	$40.783	$40.78	$40.80	$40.80
Purchase #4	$146.53	6.802%	$156.497	$156.50	$156.50	$156.50
Purchase #5	$69.86	13.445%	$79.2527	$79.25	$79.25	$79.30
Purchase #6	$85.42	10.702%	$94.5616	$94.56	$94.55	$94.60
Purchase #7	$109.53	7.866%	$118.1456	$118.15	$118.15	$118.10
7 purchase totals =	$619.62		$674.0960	$674.09	$674.10	$674.20