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	$204.40	9.596%	$224.0142	$224.01	$224.00	$224.00
Purchase #2	$163.96	10.306%	$180.8577	$180.86	$180.85	$180.90
Purchase #3	$156.69	5.671%	$165.5759	$165.58	$165.60	$165.60
Purchase #4	$125.49	8.197%	$135.7764	$135.78	$135.80	$135.80
Purchase #5	$33.89	4.192%	$35.3107	$35.31	$35.30	$35.30
Purchase #6	$162.94	9.624%	$178.6213	$178.62	$178.60	$178.60
Purchase #7	$90.46	6.625%	$96.453	$96.45	$96.45	$96.50
7 purchase totals =	$937.83		$1,016.6092	$1,016.61	$1,016.60	$1,016.70