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	$184.78	6.202%	$196.2401	$196.24	$196.25	$196.20
Purchase #2	$75.60	8.594%	$82.0971	$82.10	$82.10	$82.10
Purchase #3	$42.98	5.147%	$45.1922	$45.19	$45.20	$45.20
Purchase #4	$173.38	6.815%	$185.1958	$185.20	$185.20	$185.20
Purchase #5	$233.92	8.463%	$253.7166	$253.72	$253.70	$253.70
Purchase #6	$163.61	6.815%	$174.76	$174.76	$174.75	$174.80
Purchase #7	$90.32	13.211%	$102.2522	$102.25	$102.25	$102.30
7 purchase totals =	$964.59		$1,039.4540	$1,039.46	$1,039.45	$1,039.50