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	$162.61	9.731%	$178.4336	$178.43	$178.45	$178.40
Purchase #2	$163.92	12.794%	$184.8919	$184.89	$184.90	$184.90
Purchase #3	$10.53	7.132%	$11.281	$11.28	$11.30	$11.30
Purchase #4	$57.41	11.271%	$63.8807	$63.88	$63.90	$63.90
Purchase #5	$44.62	9.127%	$48.6925	$48.69	$48.70	$48.70
Purchase #6	$73.64	12.718%	$83.0055	$83.01	$83.00	$83.00
Purchase #7	$27.54	4.780%	$28.8564	$28.86	$28.85	$28.90
7 purchase totals =	$540.27		$599.0416	$599.04	$599.10	$599.10