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	$119.73	3.148%	$123.4991	$123.50	$123.50	$123.50
Purchase #2	$149.51	12.726%	$168.5366	$168.54	$168.55	$168.50
Purchase #3	$36.48	6.802%	$38.9614	$38.96	$38.95	$39.00
Purchase #4	$118.61	6.256%	$126.0302	$126.03	$126.05	$126.00
Purchase #5	$184.80	6.396%	$196.6198	$196.62	$196.60	$196.60
Purchase #6	$216.85	7.460%	$233.027	$233.03	$233.05	$233.00
Purchase #7	$244.51	6.165%	$259.584	$259.58	$259.60	$259.60
7 purchase totals =	$1,070.49		$1,146.2581	$1,146.26	$1,146.30	$1,146.20