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	$41.78	9.200%	$45.6238	$45.62	$45.60	$45.60
Purchase #2	$182.64	3.843%	$189.6589	$189.66	$189.65	$189.70
Purchase #3	$138.84	8.755%	$150.9954	$151.00	$151.00	$151.00
Purchase #4	$221.32	10.821%	$245.269	$245.27	$245.25	$245.30
Purchase #5	$148.89	12.594%	$167.6412	$167.64	$167.65	$167.60
Purchase #6	$176.95	4.240%	$184.4527	$184.45	$184.45	$184.50
Purchase #7	$89.30	6.827%	$95.3965	$95.40	$95.40	$95.40
7 purchase totals =	$999.72		$1,079.0375	$1,079.04	$1,079.00	$1,079.10