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	$37.85	10.670%	$41.8886	$41.89	$41.90	$41.90
Purchase #2	$150.42	7.824%	$162.1889	$162.19	$162.20	$162.20
Purchase #3	$170.97	11.658%	$190.9017	$190.90	$190.90	$190.90
Purchase #4	$56.84	10.644%	$62.89	$62.89	$62.90	$62.90
Purchase #5	$221.96	12.160%	$248.9503	$248.95	$248.95	$249.00
Purchase #6	$155.85	7.729%	$167.8956	$167.90	$167.90	$167.90
Purchase #7	$175.76	4.531%	$183.7237	$183.72	$183.70	$183.70
7 purchase totals =	$969.65		$1,058.4388	$1,058.44	$1,058.45	$1,058.50