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	$196.30	9.851%	$215.6375	$215.64	$215.65	$215.60
Purchase #2	$230.68	8.758%	$250.883	$250.88	$250.90	$250.90
Purchase #3	$64.40	13.373%	$73.0122	$73.01	$73.00	$73.00
Purchase #4	$94.70	11.273%	$105.3755	$105.38	$105.40	$105.40
Purchase #5	$73.51	12.672%	$82.8252	$82.83	$82.85	$82.80
Purchase #6	$10.63	8.749%	$11.56	$11.56	$11.55	$11.60
Purchase #7	$186.83	9.417%	$204.4238	$204.42	$204.40	$204.40
7 purchase totals =	$857.05		$943.7172	$943.72	$943.75	$943.70