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	$76.88	7.219%	$82.43	$82.43	$82.45	$82.40
Purchase #2	$13.35	11.743%	$14.9177	$14.92	$14.90	$14.90
Purchase #3	$230.57	4.602%	$241.1808	$241.18	$241.20	$241.20
Purchase #4	$27.51	3.585%	$28.4962	$28.50	$28.50	$28.50
Purchase #5	$67.77	3.844%	$70.3751	$70.38	$70.40	$70.40
Purchase #6	$247.77	9.571%	$271.4841	$271.48	$271.50	$271.50
Purchase #7	$71.86	6.728%	$76.6947	$76.69	$76.70	$76.70
7 purchase totals =	$735.71		$785.5786	$785.58	$785.65	$785.60