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	$47.75	9.465%	$52.2695	$52.27	$52.25	$52.30
Purchase #2	$53.28	10.539%	$58.8952	$58.90	$58.90	$58.90
Purchase #3	$169.82	9.154%	$185.3653	$185.37	$185.35	$185.40
Purchase #4	$80.65	12.631%	$90.8369	$90.84	$90.85	$90.80
Purchase #5	$146.86	12.773%	$165.6184	$165.62	$165.60	$165.60
Purchase #6	$34.71	13.211%	$39.2955	$39.30	$39.30	$39.30
Purchase #7	$189.98	7.740%	$204.6845	$204.68	$204.70	$204.70
7 purchase totals =	$723.05		$796.9653	$796.98	$796.95	$797.00