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	$166.61	9.761%	$182.8728	$182.87	$182.85	$182.90
Purchase #2	$46.85	10.232%	$51.6437	$51.64	$51.65	$51.60
Purchase #3	$95.27	7.294%	$102.219	$102.22	$102.20	$102.20
Purchase #4	$104.67	4.830%	$109.7256	$109.73	$109.75	$109.70
Purchase #5	$163.84	5.237%	$172.4203	$172.42	$172.40	$172.40
Purchase #6	$56.27	6.199%	$59.7582	$59.76	$59.75	$59.80
Purchase #7	$108.35	8.229%	$117.2661	$117.27	$117.25	$117.30
7 purchase totals =	$741.86		$795.9057	$795.91	$795.85	$795.90