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	$41.96	13.682%	$47.701	$47.70	$47.70	$47.70
Purchase #2	$82.48	5.144%	$86.7228	$86.72	$86.70	$86.70
Purchase #3	$5.96	7.681%	$6.4178	$6.42	$6.40	$6.40
Purchase #4	$75.32	9.388%	$82.391	$82.39	$82.40	$82.40
Purchase #5	$93.77	9.866%	$103.0213	$103.02	$103.00	$103.00
Purchase #6	$155.85	3.663%	$161.5588	$161.56	$161.55	$161.60
Purchase #7	$103.84	7.510%	$111.6384	$111.64	$111.65	$111.60
7 purchase totals =	$559.18		$599.4511	$599.45	$599.40	$599.40