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	$212.72	5.719%	$224.8855	$224.89	$224.90	$224.90
Purchase #2	$30.67	5.813%	$32.4528	$32.45	$32.45	$32.50
Purchase #3	$177.87	11.568%	$198.446	$198.45	$198.45	$198.40
Purchase #4	$13.35	9.413%	$14.6066	$14.61	$14.60	$14.60
Purchase #5	$199.41	11.338%	$222.0191	$222.02	$222.00	$222.00
Purchase #6	$154.52	6.445%	$164.4788	$164.48	$164.50	$164.50
Purchase #7	$131.97	11.400%	$147.0146	$147.01	$147.00	$147.00
7 purchase totals =	$920.51		$1,003.9034	$1,003.91	$1,003.90	$1,003.90