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	$143.67	6.187%	$152.5589	$152.56	$152.55	$152.60
Purchase #2	$74.80	9.465%	$81.8798	$81.88	$81.90	$81.90
Purchase #3	$91.34	4.190%	$95.1671	$95.17	$95.15	$95.20
Purchase #4	$204.36	10.328%	$225.4663	$225.47	$225.45	$225.50
Purchase #5	$51.38	11.725%	$57.4043	$57.40	$57.40	$57.40
Purchase #6	$210.37	13.297%	$238.3429	$238.34	$238.35	$238.30
Purchase #7	$164.35	13.727%	$186.9103	$186.91	$186.90	$186.90
7 purchase totals =	$940.27		$1,037.7296	$1,037.73	$1,037.70	$1,037.80