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	$85.66	6.449%	$91.1842	$91.18	$91.20	$91.20
Purchase #2	$244.31	4.334%	$254.8984	$254.90	$254.90	$254.90
Purchase #3	$154.94	11.186%	$172.2716	$172.27	$172.25	$172.30
Purchase #4	$191.42	11.562%	$213.552	$213.55	$213.55	$213.60
Purchase #5	$81.86	4.402%	$85.4635	$85.46	$85.45	$85.50
Purchase #6	$83.54	13.266%	$94.6224	$94.62	$94.60	$94.60
Purchase #7	$169.44	12.322%	$190.3184	$190.32	$190.30	$190.30
7 purchase totals =	$1,011.17		$1,102.3105	$1,102.30	$1,102.25	$1,102.40