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	$65.55	9.773%	$71.9562	$71.96	$71.95	$72.00
Purchase #2	$39.60	11.562%	$44.1786	$44.18	$44.20	$44.20
Purchase #3	$104.52	6.805%	$111.6326	$111.63	$111.65	$111.60
Purchase #4	$47.55	13.327%	$53.887	$53.89	$53.90	$53.90
Purchase #5	$90.56	11.259%	$100.7562	$100.76	$100.75	$100.80
Purchase #6	$171.78	6.680%	$183.2549	$183.25	$183.25	$183.30
Purchase #7	$248.58	13.179%	$281.3404	$281.34	$281.35	$281.30
7 purchase totals =	$768.14		$847.0059	$847.01	$847.05	$847.10