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	$46.38	8.426%	$50.288	$50.29	$50.30	$50.30
Purchase #2	$198.44	8.597%	$215.4999	$215.50	$215.50	$215.50
Purchase #3	$156.78	8.211%	$169.6532	$169.65	$169.65	$169.70
Purchase #4	$50.76	7.732%	$54.6848	$54.68	$54.70	$54.70
Purchase #5	$29.97	12.620%	$33.7522	$33.75	$33.75	$33.80
Purchase #6	$129.76	10.522%	$143.4133	$143.41	$143.40	$143.40
Purchase #7	$88.62	13.532%	$100.6121	$100.61	$100.60	$100.60
7 purchase totals =	$700.71		$767.9035	$767.89	$767.90	$768.00