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	$103.51	9.119%	$112.9491	$112.95	$112.95	$112.90
Purchase #2	$11.91	3.356%	$12.3097	$12.31	$12.30	$12.30
Purchase #3	$205.66	4.496%	$214.9065	$214.91	$214.90	$214.90
Purchase #4	$242.81	11.179%	$269.9537	$269.95	$269.95	$270.00
Purchase #5	$151.79	12.238%	$170.3661	$170.37	$170.35	$170.40
Purchase #6	$59.72	12.584%	$67.2352	$67.24	$67.25	$67.20
Purchase #7	$148.32	5.264%	$156.1276	$156.13	$156.15	$156.10
7 purchase totals =	$923.72		$1,003.8479	$1,003.86	$1,003.85	$1,003.80