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	$89.92	5.132%	$94.5347	$94.53	$94.55	$94.50
Purchase #2	$83.84	7.186%	$89.8647	$89.86	$89.85	$89.90
Purchase #3	$92.95	11.801%	$103.919	$103.92	$103.90	$103.90
Purchase #4	$37.94	8.602%	$41.2036	$41.20	$41.20	$41.20
Purchase #5	$10.34	5.211%	$10.8788	$10.88	$10.90	$10.90
Purchase #6	$139.71	3.518%	$144.625	$144.63	$144.65	$144.60
Purchase #7	$163.98	4.842%	$171.9199	$171.92	$171.90	$171.90
7 purchase totals =	$618.68		$656.9457	$656.94	$656.95	$656.90