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	$48.88	4.185%	$50.9256	$50.93	$50.95	$50.90
Purchase #2	$113.82	6.564%	$121.2911	$121.29	$121.30	$121.30
Purchase #3	$78.76	5.173%	$82.8343	$82.83	$82.85	$82.80
Purchase #4	$55.48	7.426%	$59.5999	$59.60	$59.60	$59.60
Purchase #5	$115.53	10.681%	$127.8698	$127.87	$127.85	$127.90
Purchase #6	$144.88	5.706%	$153.1469	$153.15	$153.15	$153.10
Purchase #7	$238.85	12.820%	$269.4706	$269.47	$269.45	$269.50
7 purchase totals =	$796.20		$865.1382	$865.14	$865.15	$865.10