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	$197.56	6.501%	$210.4034	$210.40	$210.40	$210.40
Purchase #2	$17.53	5.322%	$18.4629	$18.46	$18.45	$18.50
Purchase #3	$191.67	12.494%	$215.6172	$215.62	$215.60	$215.60
Purchase #4	$136.82	8.568%	$148.5427	$148.54	$148.55	$148.50
Purchase #5	$222.49	8.463%	$241.3193	$241.32	$241.30	$241.30
Purchase #6	$151.88	10.492%	$167.8152	$167.82	$167.80	$167.80
Purchase #7	$29.98	6.364%	$31.8879	$31.89	$31.90	$31.90
7 purchase totals =	$947.93		$1,034.0486	$1,034.05	$1,034.00	$1,034.00