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	$143.83	10.253%	$158.5769	$158.58	$158.60	$158.60
Purchase #2	$67.47	6.656%	$71.9608	$71.96	$71.95	$72.00
Purchase #3	$89.82	4.831%	$94.1592	$94.16	$94.15	$94.20
Purchase #4	$27.88	12.220%	$31.2869	$31.29	$31.30	$31.30
Purchase #5	$136.98	10.455%	$151.3013	$151.30	$151.30	$151.30
Purchase #6	$127.99	3.622%	$132.6258	$132.63	$132.65	$132.60
Purchase #7	$179.89	10.394%	$198.5878	$198.59	$198.60	$198.60
7 purchase totals =	$773.86		$838.4987	$838.51	$838.55	$838.60