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	$195.97	11.206%	$217.9304	$217.93	$217.95	$217.90
Purchase #2	$212.82	4.739%	$222.9055	$222.91	$222.90	$222.90
Purchase #3	$124.90	9.137%	$136.3121	$136.31	$136.30	$136.30
Purchase #4	$140.72	8.189%	$152.2436	$152.24	$152.25	$152.20
Purchase #5	$177.86	9.370%	$194.5255	$194.53	$194.55	$194.50
Purchase #6	$209.70	10.704%	$232.1463	$232.15	$232.15	$232.10
Purchase #7	$59.84	12.600%	$67.3798	$67.38	$67.40	$67.40
7 purchase totals =	$1,121.81		$1,223.4432	$1,223.45	$1,223.50	$1,223.30