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	$157.81	6.431%	$167.9588	$167.96	$167.95	$168.00
Purchase #2	$82.25	5.379%	$86.6742	$86.67	$86.65	$86.70
Purchase #3	$131.28	6.331%	$139.5913	$139.59	$139.60	$139.60
Purchase #4	$105.89	5.486%	$111.6991	$111.70	$111.70	$111.70
Purchase #5	$198.53	3.555%	$205.5877	$205.59	$205.60	$205.60
Purchase #6	$203.62	5.521%	$214.8619	$214.86	$214.85	$214.90
Purchase #7	$82.25	7.494%	$88.4138	$88.41	$88.40	$88.40
7 purchase totals =	$961.63		$1,014.7868	$1,014.78	$1,014.75	$1,014.90