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	$86.56	13.240%	$98.0205	$98.02	$98.00	$98.00
Purchase #2	$93.51	5.449%	$98.6054	$98.61	$98.60	$98.60
Purchase #3	$72.63	11.443%	$80.9411	$80.94	$80.95	$80.90
Purchase #4	$87.86	4.711%	$91.9991	$92.00	$92.00	$92.00
Purchase #5	$246.78	13.656%	$280.4803	$280.48	$280.50	$280.50
Purchase #6	$149.51	10.707%	$165.518	$165.52	$165.50	$165.50
Purchase #7	$67.49	4.606%	$70.5986	$70.60	$70.60	$70.60
7 purchase totals =	$804.34		$886.1630	$886.17	$886.15	$886.10