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	$127.94	4.428%	$133.6052	$133.61	$133.60	$133.60
Purchase #2	$57.50	10.548%	$63.5651	$63.57	$63.55	$63.60
Purchase #3	$52.71	3.523%	$54.567	$54.57	$54.55	$54.60
Purchase #4	$38.45	10.473%	$42.4769	$42.48	$42.50	$42.50
Purchase #5	$27.36	7.244%	$29.342	$29.34	$29.35	$29.30
Purchase #6	$80.58	9.709%	$88.4035	$88.40	$88.40	$88.40
Purchase #7	$250.41	3.156%	$258.3129	$258.31	$258.30	$258.30
7 purchase totals =	$634.95		$670.2726	$670.28	$670.25	$670.30