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	$104.67	6.150%	$111.1072	$111.11	$111.10	$111.10
Purchase #2	$53.87	6.762%	$57.5127	$57.51	$57.50	$57.50
Purchase #3	$52.88	11.753%	$59.095	$59.10	$59.10	$59.10
Purchase #4	$86.37	5.230%	$90.8872	$90.89	$90.90	$90.90
Purchase #5	$176.61	13.570%	$200.576	$200.58	$200.60	$200.60
Purchase #6	$150.59	9.768%	$165.2996	$165.30	$165.30	$165.30
Purchase #7	$19.76	10.829%	$21.8998	$21.90	$21.90	$21.90
7 purchase totals =	$644.75		$706.3775	$706.39	$706.40	$706.40