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	$183.42	8.522%	$199.0511	$199.05	$199.05	$199.10
Purchase #2	$54.46	4.505%	$56.9134	$56.91	$56.90	$56.90
Purchase #3	$84.97	11.151%	$94.445	$94.45	$94.45	$94.40
Purchase #4	$6.35	8.484%	$6.8887	$6.89	$6.90	$6.90
Purchase #5	$186.67	6.133%	$198.1185	$198.12	$198.10	$198.10
Purchase #6	$92.73	8.393%	$100.5128	$100.51	$100.50	$100.50
Purchase #7	$99.79	5.565%	$105.3433	$105.34	$105.35	$105.30
7 purchase totals =	$708.39		$761.2728	$761.27	$761.25	$761.20