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	$197.30	6.396%	$209.9193	$209.92	$209.90	$209.90
Purchase #2	$160.57	6.596%	$171.1612	$171.16	$171.15	$171.20
Purchase #3	$24.91	11.504%	$27.7756	$27.78	$27.80	$27.80
Purchase #4	$54.42	9.305%	$59.4838	$59.48	$59.50	$59.50
Purchase #5	$98.85	9.508%	$108.2487	$108.25	$108.25	$108.20
Purchase #6	$71.86	9.298%	$78.5415	$78.54	$78.55	$78.50
Purchase #7	$90.59	10.785%	$100.3601	$100.36	$100.35	$100.40
7 purchase totals =	$698.50		$755.4902	$755.49	$755.50	$755.50