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	$99.41	11.763%	$111.1036	$111.10	$111.10	$111.10
Purchase #2	$154.78	5.804%	$163.7634	$163.76	$163.75	$163.80
Purchase #3	$154.80	11.727%	$172.9534	$172.95	$172.95	$173.00
Purchase #4	$168.88	6.459%	$179.788	$179.79	$179.80	$179.80
Purchase #5	$96.86	13.135%	$109.5826	$109.58	$109.60	$109.60
Purchase #6	$52.27	3.587%	$54.1449	$54.14	$54.15	$54.10
Purchase #7	$89.86	6.655%	$95.8402	$95.84	$95.85	$95.80
7 purchase totals =	$816.86		$887.1761	$887.16	$887.20	$887.20