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	$78.25	13.815%	$89.0602	$89.06	$89.05	$89.10
Purchase #2	$109.44	12.475%	$123.0926	$123.09	$123.10	$123.10
Purchase #3	$236.32	10.567%	$261.2919	$261.29	$261.30	$261.30
Purchase #4	$185.55	3.295%	$191.6639	$191.66	$191.65	$191.70
Purchase #5	$161.84	7.254%	$173.5799	$173.58	$173.60	$173.60
Purchase #6	$138.49	13.498%	$157.1834	$157.18	$157.20	$157.20
Purchase #7	$151.58	11.609%	$169.1769	$169.18	$169.20	$169.20
7 purchase totals =	$1,061.47		$1,165.0488	$1,165.04	$1,165.10	$1,165.20