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	$90.66	4.219%	$94.4849	$94.48	$94.50	$94.50
Purchase #2	$179.75	3.431%	$185.9172	$185.92	$185.90	$185.90
Purchase #3	$98.62	6.872%	$105.3972	$105.40	$105.40	$105.40
Purchase #4	$34.67	4.685%	$36.2943	$36.29	$36.30	$36.30
Purchase #5	$203.82	4.860%	$213.7257	$213.73	$213.75	$213.70
Purchase #6	$161.88	4.142%	$168.5851	$168.59	$168.60	$168.60
Purchase #7	$61.45	8.354%	$66.5835	$66.58	$66.60	$66.60
7 purchase totals =	$830.85		$870.9879	$870.99	$871.05	$871.00