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	$128.76	10.443%	$142.2064	$142.21	$142.20	$142.20
Purchase #2	$28.59	10.617%	$31.6254	$31.63	$31.65	$31.60
Purchase #3	$82.47	8.113%	$89.1608	$89.16	$89.15	$89.20
Purchase #4	$206.28	13.179%	$233.4656	$233.47	$233.45	$233.50
Purchase #5	$14.45	5.682%	$15.271	$15.27	$15.25	$15.30
Purchase #6	$73.92	8.618%	$80.2904	$80.29	$80.30	$80.30
Purchase #7	$150.83	3.161%	$155.5977	$155.60	$155.60	$155.60
7 purchase totals =	$685.30		$747.6173	$747.63	$747.60	$747.70