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	$148.37	7.799%	$159.9414	$159.94	$159.95	$159.90
Purchase #2	$119.88	6.175%	$127.2826	$127.28	$127.30	$127.30
Purchase #3	$51.34	3.341%	$53.0553	$53.06	$53.05	$53.10
Purchase #4	$56.40	13.706%	$64.1302	$64.13	$64.15	$64.10
Purchase #5	$168.47	7.105%	$180.4398	$180.44	$180.45	$180.40
Purchase #6	$99.40	13.211%	$112.5317	$112.53	$112.55	$112.50
Purchase #7	$62.98	3.672%	$65.2926	$65.29	$65.30	$65.30
7 purchase totals =	$706.84		$762.6736	$762.67	$762.75	$762.60