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	$137.86	5.799%	$145.8545	$145.85	$145.85	$145.90
Purchase #2	$135.66	12.393%	$152.4723	$152.47	$152.45	$152.50
Purchase #3	$159.32	5.874%	$168.6785	$168.68	$168.70	$168.70
Purchase #4	$167.41	7.768%	$180.4144	$180.41	$180.40	$180.40
Purchase #5	$163.53	10.532%	$180.753	$180.75	$180.75	$180.80
Purchase #6	$126.45	12.870%	$142.7241	$142.72	$142.70	$142.70
Purchase #7	$70.99	10.279%	$78.2871	$78.29	$78.30	$78.30
7 purchase totals =	$961.22		$1,049.1839	$1,049.17	$1,049.15	$1,049.30