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	$219.48	6.313%	$233.3358	$233.34	$233.35	$233.30
Purchase #2	$62.37	5.448%	$65.7679	$65.77	$65.75	$65.80
Purchase #3	$224.80	7.580%	$241.8398	$241.84	$241.85	$241.80
Purchase #4	$37.58	11.316%	$41.8326	$41.83	$41.85	$41.80
Purchase #5	$200.90	4.676%	$210.2941	$210.29	$210.30	$210.30
Purchase #6	$44.32	4.740%	$46.4208	$46.42	$46.40	$46.40
Purchase #7	$131.93	3.673%	$136.7758	$136.78	$136.80	$136.80
7 purchase totals =	$921.38		$976.2668	$976.27	$976.30	$976.20