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	$150.97	7.792%	$162.7336	$162.73	$162.75	$162.70
Purchase #2	$128.69	3.354%	$133.0063	$133.01	$133.00	$133.00
Purchase #3	$27.81	11.714%	$31.0677	$31.07	$31.05	$31.10
Purchase #4	$127.33	10.629%	$140.8639	$140.86	$140.85	$140.90
Purchase #5	$200.73	7.178%	$215.1384	$215.14	$215.15	$215.10
Purchase #6	$133.52	12.752%	$150.5465	$150.55	$150.55	$150.50
Purchase #7	$222.85	9.446%	$243.9004	$243.90	$243.90	$243.90
7 purchase totals =	$991.90		$1,077.2568	$1,077.26	$1,077.25	$1,077.20