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	$186.53	3.236%	$192.5661	$192.57	$192.55	$192.60
Purchase #2	$53.27	5.808%	$56.3639	$56.36	$56.35	$56.40
Purchase #3	$142.53	13.723%	$162.0894	$162.09	$162.10	$162.10
Purchase #4	$167.34	7.283%	$179.5274	$179.53	$179.55	$179.50
Purchase #5	$233.98	12.102%	$262.2963	$262.30	$262.30	$262.30
Purchase #6	$64.72	8.842%	$70.4425	$70.44	$70.45	$70.40
Purchase #7	$95.79	10.228%	$105.5874	$105.59	$105.60	$105.60
7 purchase totals =	$944.16		$1,028.8730	$1,028.88	$1,028.90	$1,028.90