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	$197.56	5.647%	$208.7162	$208.72	$208.70	$208.70
Purchase #2	$72.54	3.745%	$75.2566	$75.26	$75.25	$75.30
Purchase #3	$94.95	5.491%	$100.1637	$100.16	$100.15	$100.20
Purchase #4	$43.92	6.703%	$46.864	$46.86	$46.85	$46.90
Purchase #5	$6.72	8.256%	$7.2748	$7.27	$7.25	$7.30
Purchase #6	$82.46	10.436%	$91.0655	$91.07	$91.05	$91.10
Purchase #7	$31.98	5.811%	$33.8384	$33.84	$33.85	$33.80
7 purchase totals =	$530.13		$563.1792	$563.18	$563.10	$563.30