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	$181.92	4.367%	$189.8644	$189.86	$189.85	$189.90
Purchase #2	$235.36	11.572%	$262.5959	$262.60	$262.60	$262.60
Purchase #3	$125.65	6.187%	$133.424	$133.42	$133.40	$133.40
Purchase #4	$173.59	9.119%	$189.4197	$189.42	$189.40	$189.40
Purchase #5	$181.89	4.631%	$190.3133	$190.31	$190.30	$190.30
Purchase #6	$40.25	13.601%	$45.7244	$45.72	$45.70	$45.70
Purchase #7	$80.55	6.726%	$85.9678	$85.97	$85.95	$86.00
7 purchase totals =	$1,019.21		$1,097.3095	$1,097.30	$1,097.20	$1,097.30