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	$152.59	6.361%	$162.2962	$162.30	$162.30	$162.30
Purchase #2	$12.28	7.112%	$13.1534	$13.15	$13.15	$13.20
Purchase #3	$213.43	4.302%	$222.6118	$222.61	$222.60	$222.60
Purchase #4	$114.44	9.718%	$125.5613	$125.56	$125.55	$125.60
Purchase #5	$155.71	7.272%	$167.0332	$167.03	$167.05	$167.00
Purchase #6	$19.70	8.116%	$21.2989	$21.30	$21.30	$21.30
Purchase #7	$192.65	10.314%	$212.5199	$212.52	$212.50	$212.50
7 purchase totals =	$860.80		$924.4747	$924.47	$924.45	$924.50