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	$60.64	11.182%	$67.4208	$67.42	$67.40	$67.40
Purchase #2	$244.50	10.489%	$270.1456	$270.15	$270.15	$270.10
Purchase #3	$216.67	5.664%	$228.9422	$228.94	$228.95	$228.90
Purchase #4	$80.79	5.677%	$85.3764	$85.38	$85.40	$85.40
Purchase #5	$57.25	10.868%	$63.4719	$63.47	$63.45	$63.50
Purchase #6	$72.83	7.522%	$78.3083	$78.31	$78.30	$78.30
Purchase #7	$53.64	3.535%	$55.5362	$55.54	$55.55	$55.50
7 purchase totals =	$786.32		$849.2014	$849.21	$849.20	$849.10