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	$63.27	6.839%	$67.597	$67.60	$67.60	$67.60
Purchase #2	$211.93	13.487%	$240.513	$240.51	$240.50	$240.50
Purchase #3	$237.99	3.568%	$246.4815	$246.48	$246.50	$246.50
Purchase #4	$47.33	12.255%	$53.1303	$53.13	$53.15	$53.10
Purchase #5	$234.43	4.257%	$244.4097	$244.41	$244.40	$244.40
Purchase #6	$228.51	5.702%	$241.5396	$241.54	$241.55	$241.50
Purchase #7	$30.88	6.601%	$32.9184	$32.92	$32.90	$32.90
7 purchase totals =	$1,054.34		$1,126.5895	$1,126.59	$1,126.60	$1,126.50