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	$73.80	11.437%	$82.2405	$82.24	$82.25	$82.20
Purchase #2	$18.43	7.535%	$19.8187	$19.82	$19.80	$19.80
Purchase #3	$95.35	4.707%	$99.8381	$99.84	$99.85	$99.80
Purchase #4	$234.60	8.249%	$253.9522	$253.95	$253.95	$254.00
Purchase #5	$89.73	10.227%	$98.9067	$98.91	$98.90	$98.90
Purchase #6	$175.92	9.446%	$192.5374	$192.54	$192.55	$192.50
Purchase #7	$244.38	11.502%	$272.4886	$272.49	$272.50	$272.50
7 purchase totals =	$932.21		$1,019.7822	$1,019.79	$1,019.80	$1,019.70