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	$93.52	12.511%	$105.2203	$105.22	$105.20	$105.20
Purchase #2	$18.46	9.391%	$20.1936	$20.19	$20.20	$20.20
Purchase #3	$99.78	11.482%	$111.2367	$111.24	$111.25	$111.20
Purchase #4	$95.90	8.711%	$104.2538	$104.25	$104.25	$104.30
Purchase #5	$240.40	12.143%	$269.5918	$269.59	$269.60	$269.60
Purchase #6	$111.88	6.544%	$119.2014	$119.20	$119.20	$119.20
Purchase #7	$81.35	6.398%	$86.5548	$86.55	$86.55	$86.60
7 purchase totals =	$741.29		$816.2524	$816.24	$816.25	$816.30