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	$53.54	12.844%	$60.4167	$60.42	$60.40	$60.40
Purchase #2	$177.54	11.774%	$198.4436	$198.44	$198.45	$198.40
Purchase #3	$158.49	10.328%	$174.8588	$174.86	$174.85	$174.90
Purchase #4	$193.78	3.428%	$200.4228	$200.42	$200.40	$200.40
Purchase #5	$194.93	7.727%	$209.9922	$209.99	$210.00	$210.00
Purchase #6	$85.51	5.829%	$90.4944	$90.49	$90.50	$90.50
Purchase #7	$90.26	12.638%	$101.6671	$101.67	$101.65	$101.70
7 purchase totals =	$954.05		$1,036.2956	$1,036.29	$1,036.25	$1,036.30