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	$143.75	5.570%	$151.7569	$151.76	$151.75	$151.80
Purchase #2	$213.92	6.574%	$227.9831	$227.98	$228.00	$228.00
Purchase #3	$25.64	10.753%	$28.3971	$28.40	$28.40	$28.40
Purchase #4	$19.32	8.232%	$20.9104	$20.91	$20.90	$20.90
Purchase #5	$67.90	7.146%	$72.7521	$72.75	$72.75	$72.80
Purchase #6	$129.39	5.799%	$136.8933	$136.89	$136.90	$136.90
Purchase #7	$47.53	4.399%	$49.6208	$49.62	$49.60	$49.60
7 purchase totals =	$647.45		$688.3137	$688.31	$688.30	$688.40