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	$130.25	10.341%	$143.7192	$143.72	$143.70	$143.70
Purchase #2	$6.66	9.181%	$7.2715	$7.27	$7.25	$7.30
Purchase #3	$165.41	11.609%	$184.6124	$184.61	$184.60	$184.60
Purchase #4	$123.40	7.402%	$132.5341	$132.53	$132.55	$132.50
Purchase #5	$188.83	10.807%	$209.2369	$209.24	$209.25	$209.20
Purchase #6	$131.82	6.611%	$140.5346	$140.53	$140.55	$140.50
Purchase #7	$127.85	6.428%	$136.0682	$136.07	$136.05	$136.10
7 purchase totals =	$874.22		$953.9769	$953.97	$953.95	$953.90