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	$232.34	10.420%	$256.5498	$256.55	$256.55	$256.50
Purchase #2	$55.40	9.119%	$60.4519	$60.45	$60.45	$60.50
Purchase #3	$215.38	8.601%	$233.9048	$233.90	$233.90	$233.90
Purchase #4	$181.25	8.174%	$196.0654	$196.07	$196.05	$196.10
Purchase #5	$50.52	7.695%	$54.4075	$54.41	$54.40	$54.40
Purchase #6	$129.55	11.347%	$144.25	$144.25	$144.25	$144.30
Purchase #7	$155.90	13.356%	$176.722	$176.72	$176.70	$176.70
7 purchase totals =	$1,020.34		$1,122.3514	$1,122.35	$1,122.30	$1,122.40