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	$161.49	13.463%	$183.2314	$183.23	$183.25	$183.20
Purchase #2	$144.75	13.663%	$164.5272	$164.53	$164.55	$164.50
Purchase #3	$165.98	3.760%	$172.2208	$172.22	$172.20	$172.20
Purchase #4	$32.79	8.590%	$35.6067	$35.61	$35.60	$35.60
Purchase #5	$37.45	11.781%	$41.862	$41.86	$41.85	$41.90
Purchase #6	$220.91	11.746%	$246.8581	$246.86	$246.85	$246.90
Purchase #7	$28.57	12.292%	$32.0818	$32.08	$32.10	$32.10
7 purchase totals =	$791.94		$876.3880	$876.39	$876.40	$876.40