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	$127.92	5.291%	$134.6882	$134.69	$134.70	$134.70
Purchase #2	$154.90	4.153%	$161.333	$161.33	$161.35	$161.30
Purchase #3	$48.38	6.507%	$51.5281	$51.53	$51.55	$51.50
Purchase #4	$187.36	4.804%	$196.3608	$196.36	$196.35	$196.40
Purchase #5	$103.46	9.467%	$113.2546	$113.25	$113.25	$113.30
Purchase #6	$167.79	4.138%	$174.7332	$174.73	$174.75	$174.70
Purchase #7	$92.68	7.501%	$99.6319	$99.63	$99.65	$99.60
7 purchase totals =	$882.49		$931.5298	$931.52	$931.60	$931.50