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	$213.83	12.471%	$240.4967	$240.50	$240.50	$240.50
Purchase #2	$152.96	6.468%	$162.8535	$162.85	$162.85	$162.90
Purchase #3	$108.92	11.816%	$121.79	$121.79	$121.80	$121.80
Purchase #4	$165.56	11.390%	$184.4173	$184.42	$184.40	$184.40
Purchase #5	$109.41	4.425%	$114.2514	$114.25	$114.25	$114.30
Purchase #6	$186.71	12.563%	$210.1664	$210.17	$210.15	$210.20
Purchase #7	$94.34	12.186%	$105.8363	$105.84	$105.85	$105.80
7 purchase totals =	$1,031.73		$1,139.8116	$1,139.82	$1,139.80	$1,139.90