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	$41.93	6.506%	$44.658	$44.66	$44.65	$44.70
Purchase #2	$168.60	13.171%	$190.8063	$190.81	$190.80	$190.80
Purchase #3	$75.41	4.528%	$78.8246	$78.82	$78.80	$78.80
Purchase #4	$46.78	9.469%	$51.2096	$51.21	$51.20	$51.20
Purchase #5	$110.84	5.275%	$116.6868	$116.69	$116.70	$116.70
Purchase #6	$91.81	13.517%	$104.22	$104.22	$104.20	$104.20
Purchase #7	$224.58	6.342%	$238.8229	$238.82	$238.80	$238.80
7 purchase totals =	$759.95		$825.2282	$825.23	$825.15	$825.20