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	$186.99	12.131%	$209.6738	$209.67	$209.65	$209.70
Purchase #2	$152.99	11.598%	$170.7338	$170.73	$170.75	$170.70
Purchase #3	$77.87	6.738%	$83.1169	$83.12	$83.10	$83.10
Purchase #4	$69.78	11.817%	$78.0259	$78.03	$78.05	$78.00
Purchase #5	$139.53	11.139%	$155.0722	$155.07	$155.05	$155.10
Purchase #6	$136.37	12.214%	$153.0262	$153.03	$153.05	$153.00
Purchase #7	$78.75	5.236%	$82.8734	$82.87	$82.85	$82.90
7 purchase totals =	$842.28		$932.5222	$932.52	$932.50	$932.50