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	$174.91	12.258%	$196.3505	$196.35	$196.35	$196.40
Purchase #2	$146.89	7.869%	$158.4488	$158.45	$158.45	$158.40
Purchase #3	$63.85	13.526%	$72.4864	$72.49	$72.50	$72.50
Purchase #4	$54.34	3.725%	$56.3642	$56.36	$56.35	$56.40
Purchase #5	$142.75	5.170%	$150.1302	$150.13	$150.15	$150.10
Purchase #6	$74.59	11.440%	$83.1231	$83.12	$83.10	$83.10
Purchase #7	$78.57	12.672%	$88.5264	$88.53	$88.55	$88.50
7 purchase totals =	$735.90		$805.4296	$805.43	$805.45	$805.40