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	$59.46	10.359%	$65.6195	$65.62	$65.60	$65.60
Purchase #2	$93.47	9.457%	$102.3095	$102.31	$102.30	$102.30
Purchase #3	$62.25	13.759%	$70.815	$70.82	$70.80	$70.80
Purchase #4	$6.46	3.303%	$6.6734	$6.67	$6.65	$6.70
Purchase #5	$151.52	11.360%	$168.7327	$168.73	$168.75	$168.70
Purchase #6	$105.84	3.871%	$109.9371	$109.94	$109.95	$109.90
Purchase #7	$46.53	6.689%	$49.6424	$49.64	$49.65	$49.60
7 purchase totals =	$525.53		$573.7296	$573.73	$573.70	$573.60