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	$27.75	6.481%	$29.5485	$29.55	$29.55	$29.50
Purchase #2	$28.88	7.531%	$31.055	$31.06	$31.05	$31.10
Purchase #3	$207.91	6.738%	$221.919	$221.92	$221.90	$221.90
Purchase #4	$171.50	5.851%	$181.5345	$181.53	$181.55	$181.50
Purchase #5	$100.54	10.499%	$111.0957	$111.10	$111.10	$111.10
Purchase #6	$177.47	6.589%	$189.1635	$189.16	$189.15	$189.20
Purchase #7	$73.54	7.538%	$79.0834	$79.08	$79.10	$79.10
7 purchase totals =	$787.59		$843.3996	$843.40	$843.40	$843.40