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	$75.31	3.665%	$78.0701	$78.07	$78.05	$78.10
Purchase #2	$231.38	9.480%	$253.3148	$253.31	$253.30	$253.30
Purchase #3	$51.27	4.211%	$53.429	$53.43	$53.45	$53.40
Purchase #4	$94.83	9.619%	$103.9517	$103.95	$103.95	$104.00
Purchase #5	$171.86	13.151%	$194.4613	$194.46	$194.45	$194.50
Purchase #6	$131.72	4.164%	$137.2048	$137.20	$137.20	$137.20
Purchase #7	$48.38	11.808%	$54.0927	$54.09	$54.10	$54.10
7 purchase totals =	$804.75		$874.5244	$874.51	$874.50	$874.60