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	$185.80	10.521%	$205.348	$205.35	$205.35	$205.30
Purchase #2	$219.37	13.663%	$249.3425	$249.34	$249.35	$249.30
Purchase #3	$94.45	4.492%	$98.6927	$98.69	$98.70	$98.70
Purchase #4	$59.82	8.497%	$64.9029	$64.90	$64.90	$64.90
Purchase #5	$88.31	7.744%	$95.1487	$95.15	$95.15	$95.10
Purchase #6	$245.34	4.584%	$256.5864	$256.59	$256.60	$256.60
Purchase #7	$33.55	12.746%	$37.8263	$37.83	$37.85	$37.80
7 purchase totals =	$926.64		$1,007.8475	$1,007.85	$1,007.90	$1,007.70