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	$41.68	11.673%	$46.5453	$46.55	$46.55	$46.50
Purchase #2	$180.58	8.788%	$196.4494	$196.45	$196.45	$196.40
Purchase #3	$185.64	10.873%	$205.8246	$205.82	$205.80	$205.80
Purchase #4	$153.92	9.455%	$168.4731	$168.47	$168.45	$168.50
Purchase #5	$171.61	10.538%	$189.6943	$189.69	$189.70	$189.70
Purchase #6	$90.51	5.795%	$95.7551	$95.76	$95.75	$95.80
Purchase #7	$145.36	12.572%	$163.6347	$163.63	$163.65	$163.60
7 purchase totals =	$969.30		$1,066.3765	$1,066.37	$1,066.35	$1,066.30