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	$171.26	13.695%	$194.7141	$194.71	$194.70	$194.70
Purchase #2	$81.97	4.322%	$85.5127	$85.51	$85.50	$85.50
Purchase #3	$115.67	3.312%	$119.501	$119.50	$119.50	$119.50
Purchase #4	$66.60	4.558%	$69.6356	$69.64	$69.65	$69.60
Purchase #5	$49.44	13.734%	$56.2301	$56.23	$56.25	$56.20
Purchase #6	$104.71	4.465%	$109.3853	$109.39	$109.40	$109.40
Purchase #7	$171.28	8.274%	$185.4517	$185.45	$185.45	$185.50
7 purchase totals =	$760.93		$820.4305	$820.43	$820.45	$820.40