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	$66.71	8.807%	$72.5851	$72.59	$72.60	$72.60
Purchase #2	$151.59	3.308%	$156.6046	$156.60	$156.60	$156.60
Purchase #3	$87.87	3.866%	$91.2671	$91.27	$91.25	$91.30
Purchase #4	$225.63	9.870%	$247.8997	$247.90	$247.90	$247.90
Purchase #5	$161.84	5.802%	$171.23	$171.23	$171.25	$171.20
Purchase #6	$130.89	7.565%	$140.7918	$140.79	$140.80	$140.80
Purchase #7	$118.90	3.449%	$123.0009	$123.00	$123.00	$123.00
7 purchase totals =	$943.43		$1,003.3792	$1,003.38	$1,003.40	$1,003.40