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	$150.59	7.462%	$161.827	$161.83	$161.85	$161.80
Purchase #2	$85.86	5.736%	$90.7849	$90.78	$90.80	$90.80
Purchase #3	$195.82	3.686%	$203.0379	$203.04	$203.05	$203.00
Purchase #4	$82.95	4.459%	$86.6487	$86.65	$86.65	$86.60
Purchase #5	$197.79	11.808%	$221.145	$221.15	$221.15	$221.10
Purchase #6	$146.46	9.623%	$160.5538	$160.55	$160.55	$160.60
Purchase #7	$82.80	13.459%	$93.9441	$93.94	$93.95	$93.90
7 purchase totals =	$942.27		$1,017.9414	$1,017.94	$1,018.00	$1,017.80