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	$57.26	5.829%	$60.5977	$60.60	$60.60	$60.60
Purchase #2	$173.96	12.874%	$196.3556	$196.36	$196.35	$196.40
Purchase #3	$102.49	4.410%	$107.0098	$107.01	$107.00	$107.00
Purchase #4	$138.98	9.817%	$152.6237	$152.62	$152.60	$152.60
Purchase #5	$51.71	3.564%	$53.5529	$53.55	$53.55	$53.60
Purchase #6	$78.84	13.147%	$89.2051	$89.21	$89.20	$89.20
Purchase #7	$225.31	3.574%	$233.3626	$233.36	$233.35	$233.40
7 purchase totals =	$828.55		$892.7074	$892.71	$892.65	$892.80