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	$199.29	9.540%	$218.3023	$218.30	$218.30	$218.30
Purchase #2	$222.50	11.603%	$248.3167	$248.32	$248.30	$248.30
Purchase #3	$171.31	9.288%	$187.2213	$187.22	$187.20	$187.20
Purchase #4	$91.80	11.829%	$102.659	$102.66	$102.65	$102.70
Purchase #5	$41.74	4.722%	$43.711	$43.71	$43.70	$43.70
Purchase #6	$161.64	4.296%	$168.5841	$168.58	$168.60	$168.60
Purchase #7	$52.53	4.256%	$54.7657	$54.77	$54.75	$54.80
7 purchase totals =	$940.81		$1,023.5601	$1,023.56	$1,023.50	$1,023.60