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	$73.44	4.366%	$76.6464	$76.65	$76.65	$76.60
Purchase #2	$196.53	13.786%	$223.6236	$223.62	$223.60	$223.60
Purchase #3	$84.67	4.126%	$88.1635	$88.16	$88.15	$88.20
Purchase #4	$194.88	12.185%	$218.6261	$218.63	$218.65	$218.60
Purchase #5	$179.42	6.537%	$191.1487	$191.15	$191.15	$191.10
Purchase #6	$16.94	5.752%	$17.9144	$17.91	$17.90	$17.90
Purchase #7	$82.29	8.664%	$89.4196	$89.42	$89.40	$89.40
7 purchase totals =	$828.17		$905.5423	$905.54	$905.50	$905.40