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	$123.27	7.336%	$132.3131	$132.31	$132.30	$132.30
Purchase #2	$161.32	4.455%	$168.5068	$168.51	$168.50	$168.50
Purchase #3	$142.83	12.229%	$160.2967	$160.30	$160.30	$160.30
Purchase #4	$209.86	12.459%	$236.0065	$236.01	$236.00	$236.00
Purchase #5	$53.94	10.270%	$59.4796	$59.48	$59.50	$59.50
Purchase #6	$88.45	12.722%	$99.7026	$99.70	$99.70	$99.70
Purchase #7	$229.64	9.313%	$251.0264	$251.03	$251.05	$251.00
7 purchase totals =	$1,009.31		$1,107.3317	$1,107.34	$1,107.35	$1,107.30