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	$165.89	3.683%	$171.9997	$172.00	$172.00	$172.00
Purchase #2	$167.80	7.580%	$180.5192	$180.52	$180.50	$180.50
Purchase #3	$119.97	3.285%	$123.911	$123.91	$123.90	$123.90
Purchase #4	$125.54	7.172%	$134.5437	$134.54	$134.55	$134.50
Purchase #5	$127.83	9.311%	$139.7323	$139.73	$139.75	$139.70
Purchase #6	$168.52	13.837%	$191.8381	$191.84	$191.85	$191.80
Purchase #7	$81.27	8.382%	$88.0821	$88.08	$88.10	$88.10
7 purchase totals =	$956.82		$1,030.6261	$1,030.62	$1,030.65	$1,030.50