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	$141.98	7.640%	$152.8273	$152.83	$152.85	$152.80
Purchase #2	$163.32	4.869%	$171.2721	$171.27	$171.25	$171.30
Purchase #3	$241.68	6.824%	$258.1722	$258.17	$258.15	$258.20
Purchase #4	$204.35	10.454%	$225.7127	$225.71	$225.70	$225.70
Purchase #5	$163.81	10.197%	$180.5137	$180.51	$180.50	$180.50
Purchase #6	$190.51	13.259%	$215.7697	$215.77	$215.75	$215.80
Purchase #7	$207.34	7.219%	$222.3079	$222.31	$222.30	$222.30
7 purchase totals =	$1,312.99		$1,426.5756	$1,426.57	$1,426.50	$1,426.60