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	$215.33	3.524%	$222.9182	$222.92	$222.90	$222.90
Purchase #2	$214.85	9.654%	$235.5916	$235.59	$235.60	$235.60
Purchase #3	$240.63	10.433%	$265.7349	$265.73	$265.75	$265.70
Purchase #4	$162.61	3.198%	$167.8103	$167.81	$167.80	$167.80
Purchase #5	$60.75	4.190%	$63.2954	$63.30	$63.30	$63.30
Purchase #6	$105.58	7.487%	$113.4848	$113.48	$113.50	$113.50
Purchase #7	$179.90	9.217%	$196.4814	$196.48	$196.50	$196.50
7 purchase totals =	$1,179.65		$1,265.3166	$1,265.31	$1,265.35	$1,265.30