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	$61.83	9.836%	$67.9116	$67.91	$67.90	$67.90
Purchase #2	$213.59	3.645%	$221.3754	$221.38	$221.40	$221.40
Purchase #3	$87.26	9.143%	$95.2382	$95.24	$95.25	$95.20
Purchase #4	$225.82	5.448%	$238.1227	$238.12	$238.10	$238.10
Purchase #5	$161.95	3.443%	$167.5259	$167.53	$167.55	$167.50
Purchase #6	$189.83	4.662%	$198.6799	$198.68	$198.70	$198.70
Purchase #7	$151.69	6.723%	$161.8881	$161.89	$161.90	$161.90
7 purchase totals =	$1,091.97		$1,150.7418	$1,150.75	$1,150.80	$1,150.70