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	$141.74	8.150%	$153.2918	$153.29	$153.30	$153.30
Purchase #2	$172.67	7.478%	$185.5823	$185.58	$185.60	$185.60
Purchase #3	$87.46	10.467%	$96.6144	$96.61	$96.60	$96.60
Purchase #4	$135.75	12.124%	$152.2083	$152.21	$152.20	$152.20
Purchase #5	$54.82	3.147%	$56.5452	$56.55	$56.55	$56.50
Purchase #6	$61.43	9.658%	$67.3629	$67.36	$67.35	$67.40
Purchase #7	$41.61	7.825%	$44.866	$44.87	$44.85	$44.90
7 purchase totals =	$695.48		$756.4709	$756.47	$756.45	$756.50