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	$158.98	3.548%	$164.6206	$164.62	$164.60	$164.60
Purchase #2	$156.70	6.532%	$166.9356	$166.94	$166.95	$166.90
Purchase #3	$31.54	5.821%	$33.3759	$33.38	$33.40	$33.40
Purchase #4	$121.44	6.499%	$129.3324	$129.33	$129.35	$129.30
Purchase #5	$56.94	3.636%	$59.0103	$59.01	$59.00	$59.00
Purchase #6	$118.61	11.260%	$131.9655	$131.97	$131.95	$132.00
Purchase #7	$42.30	5.286%	$44.536	$44.54	$44.55	$44.50
7 purchase totals =	$686.51		$729.7763	$729.79	$729.80	$729.70