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	$142.31	5.606%	$150.2879	$150.29	$150.30	$150.30
Purchase #2	$161.33	12.659%	$181.7528	$181.75	$181.75	$181.80
Purchase #3	$53.75	10.779%	$59.5437	$59.54	$59.55	$59.50
Purchase #4	$65.94	12.254%	$74.0203	$74.02	$74.00	$74.00
Purchase #5	$45.37	5.637%	$47.9275	$47.93	$47.95	$47.90
Purchase #6	$143.61	3.292%	$148.3376	$148.34	$148.35	$148.30
Purchase #7	$150.58	11.325%	$167.6332	$167.63	$167.65	$167.60
7 purchase totals =	$762.89		$829.5030	$829.50	$829.55	$829.40