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	$62.34	3.412%	$64.467	$64.47	$64.45	$64.50
Purchase #2	$220.79	7.620%	$237.6142	$237.61	$237.60	$237.60
Purchase #3	$189.87	5.731%	$200.7514	$200.75	$200.75	$200.80
Purchase #4	$178.39	3.483%	$184.6033	$184.60	$184.60	$184.60
Purchase #5	$140.54	8.238%	$152.1177	$152.12	$152.10	$152.10
Purchase #6	$196.35	9.539%	$215.0798	$215.08	$215.10	$215.10
Purchase #7	$184.54	6.516%	$196.5646	$196.56	$196.55	$196.60
7 purchase totals =	$1,172.82		$1,251.1980	$1,251.19	$1,251.15	$1,251.30