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	$155.74	10.261%	$171.7205	$171.72	$171.70	$171.70
Purchase #2	$32.77	10.725%	$36.2846	$36.28	$36.30	$36.30
Purchase #3	$89.47	11.522%	$99.7787	$99.78	$99.80	$99.80
Purchase #4	$232.47	5.627%	$245.5511	$245.55	$245.55	$245.60
Purchase #5	$147.46	6.641%	$157.2528	$157.25	$157.25	$157.30
Purchase #6	$133.76	10.157%	$147.346	$147.35	$147.35	$147.30
Purchase #7	$238.65	6.676%	$254.5823	$254.58	$254.60	$254.60
7 purchase totals =	$1,030.32		$1,112.5160	$1,112.51	$1,112.55	$1,112.60