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	$112.54	4.856%	$118.0049	$118.00	$118.00	$118.00
Purchase #2	$54.73	9.739%	$60.0602	$60.06	$60.05	$60.10
Purchase #3	$6.52	12.269%	$7.3199	$7.32	$7.30	$7.30
Purchase #4	$216.99	8.774%	$236.0287	$236.03	$236.05	$236.00
Purchase #5	$6.89	10.629%	$7.6223	$7.62	$7.60	$7.60
Purchase #6	$98.42	11.238%	$109.4804	$109.48	$109.50	$109.50
Purchase #7	$66.79	7.829%	$72.019	$72.02	$72.00	$72.00
7 purchase totals =	$562.88		$610.5354	$610.53	$610.50	$610.50