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	$188.42	7.562%	$202.6683	$202.67	$202.65	$202.70
Purchase #2	$18.67	11.679%	$20.8505	$20.85	$20.85	$20.90
Purchase #3	$130.32	11.666%	$145.5231	$145.52	$145.50	$145.50
Purchase #4	$82.96	9.297%	$90.6728	$90.67	$90.65	$90.70
Purchase #5	$29.73	13.725%	$33.8104	$33.81	$33.80	$33.80
Purchase #6	$153.96	13.392%	$174.5783	$174.58	$174.60	$174.60
Purchase #7	$36.28	8.709%	$39.4396	$39.44	$39.45	$39.40
7 purchase totals =	$640.34		$707.5430	$707.54	$707.50	$707.60