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	$120.72	5.430%	$127.2751	$127.28	$127.30	$127.30
Purchase #2	$212.47	8.729%	$231.0165	$231.02	$231.00	$231.00
Purchase #3	$152.67	13.456%	$173.2133	$173.21	$173.20	$173.20
Purchase #4	$181.67	12.521%	$204.4169	$204.42	$204.40	$204.40
Purchase #5	$140.85	12.425%	$158.3506	$158.35	$158.35	$158.40
Purchase #6	$82.49	5.247%	$86.8183	$86.82	$86.80	$86.80
Purchase #7	$58.54	12.639%	$65.9389	$65.94	$65.95	$65.90
7 purchase totals =	$949.41		$1,047.0296	$1,047.04	$1,047.00	$1,047.00