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	$147.50	10.361%	$162.7825	$162.78	$162.80	$162.80
Purchase #2	$131.79	6.125%	$139.8621	$139.86	$139.85	$139.90
Purchase #3	$143.61	5.847%	$152.0069	$152.01	$152.00	$152.00
Purchase #4	$159.76	7.590%	$171.8858	$171.89	$171.90	$171.90
Purchase #5	$119.68	12.108%	$134.1709	$134.17	$134.15	$134.20
Purchase #6	$194.41	7.144%	$208.2987	$208.30	$208.30	$208.30
Purchase #7	$71.61	13.106%	$80.9952	$81.00	$81.00	$81.00
7 purchase totals =	$968.36		$1,050.0021	$1,050.01	$1,050.00	$1,050.10