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	$193.81	3.271%	$200.1495	$200.15	$200.15	$200.10
Purchase #2	$154.36	9.179%	$168.5287	$168.53	$168.55	$168.50
Purchase #3	$29.45	12.841%	$33.2317	$33.23	$33.25	$33.20
Purchase #4	$113.66	12.286%	$127.6243	$127.62	$127.60	$127.60
Purchase #5	$149.40	4.212%	$155.6927	$155.69	$155.70	$155.70
Purchase #6	$215.72	5.648%	$227.9039	$227.90	$227.90	$227.90
Purchase #7	$88.91	10.331%	$98.0953	$98.10	$98.10	$98.10
7 purchase totals =	$945.31		$1,011.2261	$1,011.22	$1,011.25	$1,011.10