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	$105.28	5.662%	$111.241	$111.24	$111.25	$111.20
Purchase #2	$199.36	11.446%	$222.1787	$222.18	$222.20	$222.20
Purchase #3	$43.90	9.452%	$48.0494	$48.05	$48.05	$48.00
Purchase #4	$45.29	7.218%	$48.559	$48.56	$48.55	$48.60
Purchase #5	$162.61	13.205%	$184.0827	$184.08	$184.10	$184.10
Purchase #6	$148.86	13.364%	$168.7537	$168.75	$168.75	$168.80
Purchase #7	$23.51	5.869%	$24.8898	$24.89	$24.90	$24.90
7 purchase totals =	$728.81		$807.7543	$807.75	$807.80	$807.80