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	$153.44	7.178%	$164.4539	$164.45	$164.45	$164.50
Purchase #2	$174.78	12.110%	$195.9459	$195.95	$195.95	$195.90
Purchase #3	$167.33	6.697%	$178.5361	$178.54	$178.55	$178.50
Purchase #4	$17.69	10.505%	$19.5483	$19.55	$19.55	$19.50
Purchase #5	$168.40	6.465%	$179.2871	$179.29	$179.30	$179.30
Purchase #6	$158.82	8.631%	$172.5278	$172.53	$172.55	$172.50
Purchase #7	$95.30	10.378%	$105.1902	$105.19	$105.20	$105.20
7 purchase totals =	$935.76		$1,015.4893	$1,015.50	$1,015.55	$1,015.40