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	$136.85	6.643%	$145.9409	$145.94	$145.95	$145.90
Purchase #2	$151.84	5.361%	$159.9801	$159.98	$160.00	$160.00
Purchase #3	$248.36	5.835%	$262.8518	$262.85	$262.85	$262.90
Purchase #4	$85.77	6.135%	$91.032	$91.03	$91.05	$91.00
Purchase #5	$106.32	11.443%	$118.4862	$118.49	$118.50	$118.50
Purchase #6	$54.30	4.189%	$56.5746	$56.57	$56.55	$56.60
Purchase #7	$82.75	9.831%	$90.8852	$90.89	$90.90	$90.90
7 purchase totals =	$866.19		$925.7508	$925.75	$925.80	$925.80