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	$36.98	10.171%	$40.7412	$40.74	$40.75	$40.70
Purchase #2	$143.66	5.315%	$151.2955	$151.30	$151.30	$151.30
Purchase #3	$29.44	12.150%	$33.017	$33.02	$33.00	$33.00
Purchase #4	$167.61	12.602%	$188.7322	$188.73	$188.75	$188.70
Purchase #5	$90.77	3.672%	$94.1031	$94.10	$94.10	$94.10
Purchase #6	$84.41	5.481%	$89.0365	$89.04	$89.05	$89.00
Purchase #7	$155.41	10.458%	$171.6628	$171.66	$171.65	$171.70
7 purchase totals =	$708.28		$768.5883	$768.59	$768.60	$768.50