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	$89.41	10.180%	$98.5119	$98.51	$98.50	$98.50
Purchase #2	$33.84	6.320%	$35.9787	$35.98	$36.00	$36.00
Purchase #3	$83.47	13.638%	$94.8536	$94.85	$94.85	$94.90
Purchase #4	$20.56	5.714%	$21.7348	$21.73	$21.75	$21.70
Purchase #5	$232.39	11.359%	$258.7872	$258.79	$258.80	$258.80
Purchase #6	$131.31	12.505%	$147.7303	$147.73	$147.75	$147.70
Purchase #7	$43.78	3.849%	$45.4651	$45.47	$45.45	$45.50
7 purchase totals =	$634.76		$703.0616	$703.06	$703.10	$703.10