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	$236.65	13.199%	$267.8854	$267.89	$267.90	$267.90
Purchase #2	$64.33	6.376%	$68.4317	$68.43	$68.45	$68.40
Purchase #3	$36.60	3.511%	$37.885	$37.89	$37.90	$37.90
Purchase #4	$91.40	13.423%	$103.6686	$103.67	$103.65	$103.70
Purchase #5	$67.95	4.591%	$71.0696	$71.07	$71.05	$71.10
Purchase #6	$181.81	8.269%	$196.8439	$196.84	$196.85	$196.80
Purchase #7	$106.86	12.469%	$120.1844	$120.18	$120.20	$120.20
7 purchase totals =	$785.60		$865.9686	$865.97	$866.00	$866.00