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	$210.60	6.562%	$224.4196	$224.42	$224.40	$224.40
Purchase #2	$61.29	13.461%	$69.5402	$69.54	$69.55	$69.50
Purchase #3	$29.99	11.727%	$33.5069	$33.51	$33.50	$33.50
Purchase #4	$36.43	12.125%	$40.8471	$40.85	$40.85	$40.80
Purchase #5	$61.94	7.851%	$66.8029	$66.80	$66.80	$66.80
Purchase #6	$103.56	4.397%	$108.1135	$108.11	$108.10	$108.10
Purchase #7	$150.54	9.294%	$164.5312	$164.53	$164.55	$164.50
7 purchase totals =	$654.35		$707.7614	$707.76	$707.75	$707.60