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	$90.76	6.210%	$96.3962	$96.40	$96.40	$96.40
Purchase #2	$149.94	4.799%	$157.1356	$157.14	$157.15	$157.10
Purchase #3	$57.56	8.796%	$62.623	$62.62	$62.60	$62.60
Purchase #4	$189.76	11.834%	$212.2162	$212.22	$212.20	$212.20
Purchase #5	$132.59	7.522%	$142.5634	$142.56	$142.55	$142.60
Purchase #6	$233.32	13.781%	$265.4738	$265.47	$265.45	$265.50
Purchase #7	$88.89	13.173%	$100.5995	$100.60	$100.60	$100.60
7 purchase totals =	$942.82		$1,037.0077	$1,037.01	$1,036.95	$1,037.00