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	$199.47	11.534%	$222.4769	$222.48	$222.50	$222.50
Purchase #2	$198.57	6.843%	$212.1581	$212.16	$212.15	$212.20
Purchase #3	$162.58	7.316%	$174.4744	$174.47	$174.45	$174.50
Purchase #4	$192.42	11.811%	$215.1467	$215.15	$215.15	$215.10
Purchase #5	$155.42	11.475%	$173.2544	$173.25	$173.25	$173.30
Purchase #6	$59.61	6.228%	$63.3225	$63.32	$63.30	$63.30
Purchase #7	$115.66	11.122%	$128.5237	$128.52	$128.50	$128.50
7 purchase totals =	$1,083.73		$1,189.3567	$1,189.35	$1,189.30	$1,189.40