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	$49.72	7.307%	$53.353	$53.35	$53.35	$53.40
Purchase #2	$114.74	7.431%	$123.2663	$123.27	$123.25	$123.30
Purchase #3	$27.57	12.848%	$31.1122	$31.11	$31.10	$31.10
Purchase #4	$171.37	6.406%	$182.348	$182.35	$182.35	$182.30
Purchase #5	$51.37	10.189%	$56.6041	$56.60	$56.60	$56.60
Purchase #6	$38.41	10.304%	$42.3678	$42.37	$42.35	$42.40
Purchase #7	$52.43	13.603%	$59.5621	$59.56	$59.55	$59.60
7 purchase totals =	$505.61		$548.6135	$548.61	$548.55	$548.70