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	$76.78	4.734%	$80.4148	$80.41	$80.40	$80.40
Purchase #2	$18.86	3.640%	$19.5465	$19.55	$19.55	$19.50
Purchase #3	$49.53	5.469%	$52.2388	$52.24	$52.25	$52.20
Purchase #4	$145.57	4.786%	$152.537	$152.54	$152.55	$152.50
Purchase #5	$38.86	9.495%	$42.5498	$42.55	$42.55	$42.50
Purchase #6	$194.33	13.248%	$220.0748	$220.07	$220.05	$220.10
Purchase #7	$189.90	12.292%	$213.2425	$213.24	$213.25	$213.20
7 purchase totals =	$713.83		$780.6042	$780.60	$780.60	$780.40