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	$94.89	8.355%	$102.8181	$102.82	$102.80	$102.80
Purchase #2	$125.70	12.556%	$141.4829	$141.48	$141.50	$141.50
Purchase #3	$78.80	3.226%	$81.3421	$81.34	$81.35	$81.30
Purchase #4	$179.91	9.220%	$196.4977	$196.50	$196.50	$196.50
Purchase #5	$166.38	4.113%	$173.2232	$173.22	$173.20	$173.20
Purchase #6	$99.48	12.292%	$111.7081	$111.71	$111.70	$111.70
Purchase #7	$142.66	3.290%	$147.3535	$147.35	$147.35	$147.40
7 purchase totals =	$887.82		$954.4256	$954.42	$954.40	$954.40