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	$140.87	9.337%	$154.023	$154.02	$154.00	$154.00
Purchase #2	$175.58	11.621%	$195.9842	$195.98	$196.00	$196.00
Purchase #3	$83.49	7.263%	$89.5539	$89.55	$89.55	$89.60
Purchase #4	$37.51	13.310%	$42.5026	$42.50	$42.50	$42.50
Purchase #5	$83.97	10.116%	$92.4644	$92.46	$92.45	$92.50
Purchase #6	$195.67	4.578%	$204.6278	$204.63	$204.65	$204.60
Purchase #7	$149.72	3.725%	$155.2971	$155.30	$155.30	$155.30
7 purchase totals =	$866.81		$934.4530	$934.44	$934.45	$934.50