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	$91.26	3.616%	$94.56	$94.56	$94.55	$94.60
Purchase #2	$112.97	5.657%	$119.3607	$119.36	$119.35	$119.40
Purchase #3	$141.90	7.707%	$152.8362	$152.84	$152.85	$152.80
Purchase #4	$89.65	10.368%	$98.9449	$98.94	$98.95	$98.90
Purchase #5	$192.45	8.849%	$209.4799	$209.48	$209.50	$209.50
Purchase #6	$125.59	5.788%	$132.8591	$132.86	$132.85	$132.90
Purchase #7	$39.42	3.783%	$40.9113	$40.91	$40.90	$40.90
7 purchase totals =	$793.24		$848.9521	$848.95	$848.95	$849.00