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	$78.88	4.145%	$82.1496	$82.15	$82.15	$82.10
Purchase #2	$103.76	5.311%	$109.2707	$109.27	$109.25	$109.30
Purchase #3	$48.29	7.415%	$51.8707	$51.87	$51.85	$51.90
Purchase #4	$73.31	10.385%	$80.9232	$80.92	$80.90	$80.90
Purchase #5	$118.54	13.115%	$134.0865	$134.09	$134.10	$134.10
Purchase #6	$209.43	3.702%	$217.1831	$217.18	$217.20	$217.20
Purchase #7	$25.58	12.258%	$28.7156	$28.72	$28.70	$28.70
7 purchase totals =	$657.79		$704.1994	$704.20	$704.15	$704.20