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	$32.93	6.485%	$35.0655	$35.07	$35.05	$35.10
Purchase #2	$40.78	7.659%	$43.9033	$43.90	$43.90	$43.90
Purchase #3	$155.76	3.106%	$160.5979	$160.60	$160.60	$160.60
Purchase #4	$96.44	3.729%	$100.0362	$100.04	$100.05	$100.00
Purchase #5	$235.59	11.563%	$262.8313	$262.83	$262.85	$262.80
Purchase #6	$130.97	6.179%	$139.0626	$139.06	$139.05	$139.10
Purchase #7	$197.87	5.690%	$209.1288	$209.13	$209.15	$209.10
7 purchase totals =	$890.34		$950.6256	$950.63	$950.65	$950.60