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	$204.67	9.237%	$223.5754	$223.58	$223.60	$223.60
Purchase #2	$78.60	5.537%	$82.9521	$82.95	$82.95	$83.00
Purchase #3	$242.74	7.303%	$260.4673	$260.47	$260.45	$260.50
Purchase #4	$100.93	10.740%	$111.7699	$111.77	$111.75	$111.80
Purchase #5	$27.51	3.102%	$28.3634	$28.36	$28.35	$28.40
Purchase #6	$196.27	4.782%	$205.6556	$205.66	$205.65	$205.70
Purchase #7	$175.36	7.344%	$188.2384	$188.24	$188.25	$188.20
7 purchase totals =	$1,026.08		$1,101.0221	$1,101.03	$1,101.00	$1,101.20