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	$168.59	9.799%	$185.1101	$185.11	$185.10	$185.10
Purchase #2	$113.27	11.819%	$126.6574	$126.66	$126.65	$126.70
Purchase #3	$29.79	4.225%	$31.0486	$31.05	$31.05	$31.00
Purchase #4	$240.73	13.210%	$272.5304	$272.53	$272.55	$272.50
Purchase #5	$234.48	3.311%	$242.2436	$242.24	$242.25	$242.20
Purchase #6	$80.57	12.442%	$90.5945	$90.59	$90.60	$90.60
Purchase #7	$178.39	7.647%	$192.0315	$192.03	$192.05	$192.00
7 purchase totals =	$1,045.82		$1,140.2161	$1,140.21	$1,140.25	$1,140.10