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	$101.33	4.760%	$106.1533	$106.15	$106.15	$106.20
Purchase #2	$121.52	10.177%	$133.8871	$133.89	$133.90	$133.90
Purchase #3	$105.63	12.320%	$118.6436	$118.64	$118.65	$118.60
Purchase #4	$216.77	12.524%	$243.9183	$243.92	$243.90	$243.90
Purchase #5	$6.39	7.763%	$6.8861	$6.89	$6.90	$6.90
Purchase #6	$233.43	3.489%	$241.5744	$241.57	$241.55	$241.60
Purchase #7	$83.39	8.249%	$90.2688	$90.27	$90.25	$90.30
7 purchase totals =	$868.46		$941.3316	$941.33	$941.30	$941.40