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	$95.37	5.109%	$100.2425	$100.24	$100.25	$100.20
Purchase #2	$29.99	6.748%	$32.0137	$32.01	$32.00	$32.00
Purchase #3	$68.98	4.369%	$71.9937	$71.99	$72.00	$72.00
Purchase #4	$38.99	9.267%	$42.6032	$42.60	$42.60	$42.60
Purchase #5	$104.63	5.189%	$110.0593	$110.06	$110.05	$110.10
Purchase #6	$60.61	6.217%	$64.3781	$64.38	$64.40	$64.40
Purchase #7	$38.92	9.419%	$42.5859	$42.59	$42.60	$42.60
7 purchase totals =	$437.49		$463.8764	$463.87	$463.90	$463.90