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	$223.79	8.847%	$243.5887	$243.59	$243.60	$243.60
Purchase #2	$167.96	4.239%	$175.0798	$175.08	$175.10	$175.10
Purchase #3	$73.72	12.441%	$82.8915	$82.89	$82.90	$82.90
Purchase #4	$204.31	3.136%	$210.7172	$210.72	$210.70	$210.70
Purchase #5	$110.51	13.189%	$125.0852	$125.09	$125.10	$125.10
Purchase #6	$230.41	5.535%	$243.1632	$243.16	$243.15	$243.20
Purchase #7	$5.31	7.521%	$5.7094	$5.71	$5.70	$5.70
7 purchase totals =	$1,016.01		$1,086.2350	$1,086.24	$1,086.25	$1,086.30