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	$229.94	8.602%	$249.7194	$249.72	$249.70	$249.70
Purchase #2	$33.56	8.719%	$36.4861	$36.49	$36.50	$36.50
Purchase #3	$99.65	10.247%	$109.8611	$109.86	$109.85	$109.90
Purchase #4	$172.71	4.168%	$179.9086	$179.91	$179.90	$179.90
Purchase #5	$75.51	13.293%	$85.5475	$85.55	$85.55	$85.50
Purchase #6	$168.53	10.504%	$186.2324	$186.23	$186.25	$186.20
Purchase #7	$205.84	8.107%	$222.5274	$222.53	$222.55	$222.50
7 purchase totals =	$985.74		$1,070.2825	$1,070.29	$1,070.30	$1,070.20