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	$193.25	8.799%	$210.2541	$210.25	$210.25	$210.30
Purchase #2	$217.70	12.586%	$245.0997	$245.10	$245.10	$245.10
Purchase #3	$87.51	4.360%	$91.3254	$91.33	$91.35	$91.30
Purchase #4	$87.43	4.565%	$91.4212	$91.42	$91.40	$91.40
Purchase #5	$57.43	11.332%	$63.938	$63.94	$63.95	$63.90
Purchase #6	$166.78	12.141%	$187.0288	$187.03	$187.05	$187.00
Purchase #7	$165.40	4.524%	$172.8827	$172.88	$172.90	$172.90
7 purchase totals =	$975.50		$1,061.9499	$1,061.95	$1,062.00	$1,061.90