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	$40.51	6.189%	$43.0172	$43.02	$43.00	$43.00
Purchase #2	$185.80	12.247%	$208.5549	$208.55	$208.55	$208.60
Purchase #3	$52.64	12.391%	$59.1626	$59.16	$59.15	$59.20
Purchase #4	$241.54	10.400%	$266.6602	$266.66	$266.65	$266.70
Purchase #5	$61.76	10.144%	$68.0249	$68.02	$68.00	$68.00
Purchase #6	$200.99	11.516%	$224.136	$224.14	$224.15	$224.10
Purchase #7	$249.98	11.322%	$278.2827	$278.28	$278.30	$278.30
7 purchase totals =	$1,033.22		$1,147.8385	$1,147.83	$1,147.80	$1,147.90