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	$193.41	10.590%	$213.8921	$213.89	$213.90	$213.90
Purchase #2	$213.85	4.603%	$223.6935	$223.69	$223.70	$223.70
Purchase #3	$246.82	3.528%	$255.5278	$255.53	$255.55	$255.50
Purchase #4	$55.64	11.242%	$61.895	$61.90	$61.90	$61.90
Purchase #5	$6.68	10.566%	$7.3858	$7.39	$7.40	$7.40
Purchase #6	$196.41	3.110%	$202.5184	$202.52	$202.50	$202.50
Purchase #7	$104.57	5.413%	$110.2304	$110.23	$110.25	$110.20
7 purchase totals =	$1,017.38		$1,075.1430	$1,075.15	$1,075.20	$1,075.10