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	$237.57	7.710%	$255.8866	$255.89	$255.90	$255.90
Purchase #2	$77.45	3.234%	$79.9547	$79.95	$79.95	$80.00
Purchase #3	$101.68	7.731%	$109.5409	$109.54	$109.55	$109.50
Purchase #4	$38.77	6.313%	$41.2176	$41.22	$41.20	$41.20
Purchase #5	$239.32	8.467%	$259.5832	$259.58	$259.60	$259.60
Purchase #6	$28.68	8.661%	$31.164	$31.16	$31.15	$31.20
Purchase #7	$174.47	6.401%	$185.6378	$185.64	$185.65	$185.60
7 purchase totals =	$897.94		$962.9848	$962.98	$963.00	$963.00