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	$181.50	12.440%	$204.0786	$204.08	$204.10	$204.10
Purchase #2	$147.97	7.127%	$158.5158	$158.52	$158.50	$158.50
Purchase #3	$232.84	5.856%	$246.4751	$246.48	$246.50	$246.50
Purchase #4	$42.83	10.766%	$47.4411	$47.44	$47.45	$47.40
Purchase #5	$65.98	9.561%	$72.2883	$72.29	$72.30	$72.30
Purchase #6	$74.31	12.565%	$83.6471	$83.65	$83.65	$83.60
Purchase #7	$223.81	13.198%	$253.3484	$253.35	$253.35	$253.30
7 purchase totals =	$969.24		$1,065.7944	$1,065.81	$1,065.85	$1,065.70