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	$82.45	8.686%	$89.6116	$89.61	$89.60	$89.60
Purchase #2	$11.64	4.764%	$12.1945	$12.19	$12.20	$12.20
Purchase #3	$30.60	9.794%	$33.597	$33.60	$33.60	$33.60
Purchase #4	$231.60	4.612%	$242.2814	$242.28	$242.30	$242.30
Purchase #5	$78.36	7.583%	$84.302	$84.30	$84.30	$84.30
Purchase #6	$140.65	8.671%	$152.8458	$152.85	$152.85	$152.80
Purchase #7	$105.82	13.337%	$119.9332	$119.93	$119.95	$119.90
7 purchase totals =	$681.12		$734.7655	$734.76	$734.80	$734.70