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	$78.32	5.270%	$82.4475	$82.45	$82.45	$82.40
Purchase #2	$77.49	7.181%	$83.0546	$83.05	$83.05	$83.10
Purchase #3	$164.97	6.155%	$175.1239	$175.12	$175.10	$175.10
Purchase #4	$31.72	6.458%	$33.7685	$33.77	$33.75	$33.80
Purchase #5	$232.80	12.183%	$261.162	$261.16	$261.15	$261.20
Purchase #6	$52.62	11.338%	$58.5861	$58.59	$58.60	$58.60
Purchase #7	$96.33	11.519%	$107.4263	$107.43	$107.45	$107.40
7 purchase totals =	$734.25		$801.5689	$801.57	$801.55	$801.60