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	$57.56	6.780%	$61.4626	$61.46	$61.45	$61.50
Purchase #2	$152.94	12.202%	$171.6017	$171.60	$171.60	$171.60
Purchase #3	$219.62	6.670%	$234.2687	$234.27	$234.25	$234.30
Purchase #4	$222.77	10.347%	$245.82	$245.82	$245.80	$245.80
Purchase #5	$121.58	8.638%	$132.0821	$132.08	$132.10	$132.10
Purchase #6	$65.50	10.382%	$72.3002	$72.30	$72.30	$72.30
Purchase #7	$167.37	4.872%	$175.5243	$175.52	$175.50	$175.50
7 purchase totals =	$1,007.34		$1,093.0596	$1,093.05	$1,093.00	$1,093.10