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	$64.69	7.484%	$69.5314	$69.53	$69.55	$69.50
Purchase #2	$99.82	7.703%	$107.5091	$107.51	$107.50	$107.50
Purchase #3	$57.63	8.156%	$62.3303	$62.33	$62.35	$62.30
Purchase #4	$34.68	7.794%	$37.383	$37.38	$37.40	$37.40
Purchase #5	$96.87	7.785%	$104.4113	$104.41	$104.40	$104.40
Purchase #6	$240.30	8.724%	$261.2638	$261.26	$261.25	$261.30
Purchase #7	$82.84	9.143%	$90.4141	$90.41	$90.40	$90.40
7 purchase totals =	$676.83		$732.8430	$732.83	$732.85	$732.80