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	$85.72	6.104%	$90.9523	$90.95	$90.95	$91.00
Purchase #2	$109.38	4.420%	$114.2146	$114.21	$114.20	$114.20
Purchase #3	$73.46	4.152%	$76.5101	$76.51	$76.50	$76.50
Purchase #4	$128.69	4.402%	$134.3549	$134.35	$134.35	$134.40
Purchase #5	$95.67	13.139%	$108.2401	$108.24	$108.25	$108.20
Purchase #6	$6.54	7.618%	$7.0382	$7.04	$7.05	$7.00
Purchase #7	$224.88	3.616%	$233.0117	$233.01	$233.00	$233.00
7 purchase totals =	$724.34		$764.3219	$764.31	$764.30	$764.30