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	$139.74	9.667%	$153.2487	$153.25	$153.25	$153.20
Purchase #2	$156.83	8.360%	$169.941	$169.94	$169.95	$169.90
Purchase #3	$216.38	11.320%	$240.8742	$240.87	$240.85	$240.90
Purchase #4	$88.76	8.472%	$96.2797	$96.28	$96.30	$96.30
Purchase #5	$82.80	8.496%	$89.8347	$89.83	$89.85	$89.80
Purchase #6	$92.92	10.857%	$103.0083	$103.01	$103.00	$103.00
Purchase #7	$188.35	6.395%	$200.395	$200.40	$200.40	$200.40
7 purchase totals =	$965.78		$1,053.5816	$1,053.58	$1,053.60	$1,053.50