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	$205.56	8.812%	$223.6739	$223.67	$223.65	$223.70
Purchase #2	$149.40	10.180%	$164.6089	$164.61	$164.60	$164.60
Purchase #3	$144.97	6.294%	$154.0944	$154.09	$154.10	$154.10
Purchase #4	$232.71	9.682%	$255.241	$255.24	$255.25	$255.20
Purchase #5	$69.59	12.176%	$78.0633	$78.06	$78.05	$78.10
Purchase #6	$207.86	12.236%	$233.2937	$233.29	$233.30	$233.30
Purchase #7	$203.73	10.144%	$224.3964	$224.40	$224.40	$224.40
7 purchase totals =	$1,213.82		$1,333.3716	$1,333.36	$1,333.35	$1,333.40