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	$66.48	12.588%	$74.8485	$74.85	$74.85	$74.80
Purchase #2	$24.93	9.862%	$27.3886	$27.39	$27.40	$27.40
Purchase #3	$89.61	13.636%	$101.8292	$101.83	$101.85	$101.80
Purchase #4	$200.54	3.493%	$207.5449	$207.54	$207.55	$207.50
Purchase #5	$57.55	6.595%	$61.3454	$61.35	$61.35	$61.30
Purchase #6	$153.27	12.718%	$172.7629	$172.76	$172.75	$172.80
Purchase #7	$28.27	11.495%	$31.5196	$31.52	$31.50	$31.50
7 purchase totals =	$620.65		$677.2391	$677.24	$677.25	$677.10