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	$217.98	4.674%	$228.1684	$228.17	$228.15	$228.20
Purchase #2	$60.37	3.364%	$62.4008	$62.40	$62.40	$62.40
Purchase #3	$97.89	13.229%	$110.8399	$110.84	$110.85	$110.80
Purchase #4	$57.48	7.502%	$61.7921	$61.79	$61.80	$61.80
Purchase #5	$229.31	7.625%	$246.7949	$246.79	$246.80	$246.80
Purchase #6	$123.94	6.330%	$131.7854	$131.79	$131.80	$131.80
Purchase #7	$153.91	13.186%	$174.2046	$174.20	$174.20	$174.20
7 purchase totals =	$940.88		$1,015.9861	$1,015.98	$1,016.00	$1,016.00