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	$62.98	7.746%	$67.8584	$67.86	$67.85	$67.90
Purchase #2	$79.94	13.317%	$90.5856	$90.59	$90.60	$90.60
Purchase #3	$100.40	12.137%	$112.5855	$112.59	$112.60	$112.60
Purchase #4	$110.96	11.511%	$123.7326	$123.73	$123.75	$123.70
Purchase #5	$178.97	7.527%	$192.4411	$192.44	$192.45	$192.40
Purchase #6	$183.40	12.453%	$206.2388	$206.24	$206.25	$206.20
Purchase #7	$139.61	6.526%	$148.7209	$148.72	$148.70	$148.70
7 purchase totals =	$856.26		$942.1629	$942.17	$942.20	$942.10