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	$223.73	4.745%	$234.346	$234.35	$234.35	$234.30
Purchase #2	$208.54	12.663%	$234.9474	$234.95	$234.95	$234.90
Purchase #3	$248.30	13.294%	$281.309	$281.31	$281.30	$281.30
Purchase #4	$56.56	7.652%	$60.888	$60.89	$60.90	$60.90
Purchase #5	$240.94	13.267%	$272.9055	$272.91	$272.90	$272.90
Purchase #6	$150.41	7.714%	$162.0126	$162.01	$162.00	$162.00
Purchase #7	$90.96	10.119%	$100.1642	$100.16	$100.15	$100.20
7 purchase totals =	$1,219.44		$1,346.5727	$1,346.58	$1,346.55	$1,346.50