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	$212.75	3.731%	$220.6877	$220.69	$220.70	$220.70
Purchase #2	$217.62	3.138%	$224.4489	$224.45	$224.45	$224.40
Purchase #3	$70.33	11.245%	$78.2386	$78.24	$78.25	$78.20
Purchase #4	$106.88	10.786%	$118.4081	$118.41	$118.40	$118.40
Purchase #5	$67.70	3.745%	$70.2354	$70.24	$70.25	$70.20
Purchase #6	$231.59	10.367%	$255.5989	$255.60	$255.60	$255.60
Purchase #7	$115.73	3.502%	$119.7829	$119.78	$119.80	$119.80
7 purchase totals =	$1,022.60		$1,087.4005	$1,087.41	$1,087.45	$1,087.30