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	$170.96	11.700%	$190.9623	$190.96	$190.95	$191.00
Purchase #2	$113.82	9.421%	$124.543	$124.54	$124.55	$124.50
Purchase #3	$244.95	7.447%	$263.1914	$263.19	$263.20	$263.20
Purchase #4	$182.61	7.589%	$196.4683	$196.47	$196.45	$196.50
Purchase #5	$250.78	12.574%	$282.3131	$282.31	$282.30	$282.30
Purchase #6	$82.79	4.393%	$86.427	$86.43	$86.45	$86.40
Purchase #7	$190.67	10.226%	$210.1679	$210.17	$210.15	$210.20
7 purchase totals =	$1,236.58		$1,354.0730	$1,354.07	$1,354.05	$1,354.10