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	$210.82	3.510%	$218.2198	$218.22	$218.20	$218.20
Purchase #2	$62.48	11.870%	$69.8964	$69.90	$69.90	$69.90
Purchase #3	$126.96	10.269%	$139.9975	$140.00	$140.00	$140.00
Purchase #4	$79.62	3.342%	$82.2809	$82.28	$82.30	$82.30
Purchase #5	$134.82	12.286%	$151.384	$151.38	$151.40	$151.40
Purchase #6	$199.25	5.342%	$209.8939	$209.89	$209.90	$209.90
Purchase #7	$128.60	8.511%	$139.5451	$139.55	$139.55	$139.50
7 purchase totals =	$942.55		$1,011.2176	$1,011.22	$1,011.25	$1,011.20