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	$126.70	5.671%	$133.8852	$133.89	$133.90	$133.90
Purchase #2	$147.37	4.471%	$153.9589	$153.96	$153.95	$154.00
Purchase #3	$37.33	12.517%	$42.0026	$42.00	$42.00	$42.00
Purchase #4	$52.64	8.870%	$57.3092	$57.31	$57.30	$57.30
Purchase #5	$114.29	8.383%	$123.8709	$123.87	$123.85	$123.90
Purchase #6	$106.57	12.557%	$119.952	$119.95	$119.95	$120.00
Purchase #7	$51.98	12.706%	$58.5846	$58.58	$58.60	$58.60
7 purchase totals =	$636.88		$689.5634	$689.56	$689.55	$689.70