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	$100.53	11.827%	$112.4197	$112.42	$112.40	$112.40
Purchase #2	$131.68	11.211%	$146.4426	$146.44	$146.45	$146.40
Purchase #3	$55.99	5.549%	$59.0969	$59.10	$59.10	$59.10
Purchase #4	$220.46	4.435%	$230.2374	$230.24	$230.25	$230.20
Purchase #5	$221.58	6.393%	$235.7456	$235.75	$235.75	$235.70
Purchase #6	$187.76	12.118%	$210.5128	$210.51	$210.50	$210.50
Purchase #7	$131.93	3.794%	$136.9354	$136.94	$136.95	$136.90
7 purchase totals =	$1,049.93		$1,131.3904	$1,131.40	$1,131.40	$1,131.20