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	$99.37	10.309%	$109.6141	$109.61	$109.60	$109.60
Purchase #2	$245.79	8.339%	$266.2864	$266.29	$266.30	$266.30
Purchase #3	$78.25	10.695%	$86.6188	$86.62	$86.60	$86.60
Purchase #4	$177.46	4.259%	$185.018	$185.02	$185.00	$185.00
Purchase #5	$143.55	3.462%	$148.5197	$148.52	$148.50	$148.50
Purchase #6	$95.32	10.873%	$105.6841	$105.68	$105.70	$105.70
Purchase #7	$233.62	12.588%	$263.0281	$263.03	$263.05	$263.00
7 purchase totals =	$1,073.36		$1,164.7692	$1,164.77	$1,164.75	$1,164.70