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	$143.71	4.855%	$150.6871	$150.69	$150.70	$150.70
Purchase #2	$137.33	3.525%	$142.1709	$142.17	$142.15	$142.20
Purchase #3	$86.90	10.636%	$96.1427	$96.14	$96.15	$96.10
Purchase #4	$227.90	3.687%	$236.3027	$236.30	$236.30	$236.30
Purchase #5	$108.33	13.605%	$123.0683	$123.07	$123.05	$123.10
Purchase #6	$197.78	3.686%	$205.0702	$205.07	$205.05	$205.10
Purchase #7	$16.93	7.272%	$18.1611	$18.16	$18.15	$18.20
7 purchase totals =	$918.88		$971.6030	$971.60	$971.55	$971.70