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	$212.59	10.439%	$234.7823	$234.78	$234.80	$234.80
Purchase #2	$185.44	8.183%	$200.6146	$200.61	$200.60	$200.60
Purchase #3	$172.69	5.197%	$181.6647	$181.66	$181.65	$181.70
Purchase #4	$75.29	6.343%	$80.0656	$80.07	$80.05	$80.10
Purchase #5	$85.35	5.216%	$89.8019	$89.80	$89.80	$89.80
Purchase #6	$119.45	12.654%	$134.5652	$134.57	$134.55	$134.60
Purchase #7	$119.95	9.447%	$131.2817	$131.28	$131.30	$131.30
7 purchase totals =	$970.76		$1,052.7760	$1,052.77	$1,052.75	$1,052.90