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	$71.76	9.328%	$78.4538	$78.45	$78.45	$78.50
Purchase #2	$161.99	11.813%	$181.1259	$181.13	$181.15	$181.10
Purchase #3	$124.44	12.573%	$140.0858	$140.09	$140.10	$140.10
Purchase #4	$93.92	10.206%	$103.5055	$103.51	$103.50	$103.50
Purchase #5	$147.94	6.281%	$157.2321	$157.23	$157.25	$157.20
Purchase #6	$199.79	8.518%	$216.8081	$216.81	$216.80	$216.80
Purchase #7	$112.76	13.756%	$128.2713	$128.27	$128.25	$128.30
7 purchase totals =	$912.60		$1,005.4825	$1,005.49	$1,005.50	$1,005.50