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	$197.30	5.695%	$208.5362	$208.54	$208.55	$208.50
Purchase #2	$37.49	13.216%	$42.4447	$42.44	$42.45	$42.40
Purchase #3	$210.98	3.112%	$217.5457	$217.55	$217.55	$217.50
Purchase #4	$247.37	3.836%	$256.8591	$256.86	$256.85	$256.90
Purchase #5	$160.96	4.458%	$168.1356	$168.14	$168.15	$168.10
Purchase #6	$58.47	9.293%	$63.9036	$63.90	$63.90	$63.90
Purchase #7	$14.89	3.735%	$15.4461	$15.45	$15.45	$15.40
7 purchase totals =	$927.46		$972.8710	$972.88	$972.90	$972.70