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	$180.30	11.167%	$200.4341	$200.43	$200.45	$200.40
Purchase #2	$66.47	7.392%	$71.3835	$71.38	$71.40	$71.40
Purchase #3	$97.28	5.784%	$102.9067	$102.91	$102.90	$102.90
Purchase #4	$186.72	12.678%	$210.3924	$210.39	$210.40	$210.40
Purchase #5	$43.69	5.854%	$46.2476	$46.25	$46.25	$46.20
Purchase #6	$172.32	7.756%	$185.6851	$185.69	$185.70	$185.70
Purchase #7	$190.84	12.650%	$214.9813	$214.98	$215.00	$215.00
7 purchase totals =	$937.62		$1,032.0307	$1,032.03	$1,032.10	$1,032.00