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	$195.75	4.607%	$204.7682	$204.77	$204.75	$204.80
Purchase #2	$36.68	13.228%	$41.532	$41.53	$41.55	$41.50
Purchase #3	$55.81	13.446%	$63.3142	$63.31	$63.30	$63.30
Purchase #4	$135.50	4.475%	$141.5636	$141.56	$141.55	$141.60
Purchase #5	$152.98	3.645%	$158.5561	$158.56	$158.55	$158.60
Purchase #6	$35.41	8.749%	$38.508	$38.51	$38.50	$38.50
Purchase #7	$86.86	3.701%	$90.0747	$90.07	$90.05	$90.10
7 purchase totals =	$698.99		$738.3168	$738.31	$738.25	$738.40