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	$35.59	4.216%	$37.0905	$37.09	$37.10	$37.10
Purchase #2	$40.32	7.232%	$43.2359	$43.24	$43.25	$43.20
Purchase #3	$159.52	3.165%	$164.5688	$164.57	$164.55	$164.60
Purchase #4	$30.81	6.646%	$32.8576	$32.86	$32.85	$32.90
Purchase #5	$16.32	12.587%	$18.3742	$18.37	$18.35	$18.40
Purchase #6	$23.25	3.482%	$24.0596	$24.06	$24.05	$24.10
Purchase #7	$178.80	8.449%	$193.9068	$193.91	$193.90	$193.90
7 purchase totals =	$484.61		$514.0934	$514.10	$514.05	$514.20