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	$84.84	9.165%	$92.6156	$92.62	$92.60	$92.60
Purchase #2	$156.63	5.103%	$164.6228	$164.62	$164.60	$164.60
Purchase #3	$121.88	4.461%	$127.3171	$127.32	$127.30	$127.30
Purchase #4	$182.62	6.535%	$194.5542	$194.55	$194.55	$194.60
Purchase #5	$194.72	9.689%	$213.5864	$213.59	$213.60	$213.60
Purchase #6	$189.45	8.448%	$205.4547	$205.45	$205.45	$205.50
Purchase #7	$56.31	6.358%	$59.8902	$59.89	$59.90	$59.90
7 purchase totals =	$986.45		$1,058.0410	$1,058.04	$1,058.00	$1,058.10