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	$64.90	8.654%	$70.5164	$70.52	$70.50	$70.50
Purchase #2	$153.59	9.510%	$168.1964	$168.20	$168.20	$168.20
Purchase #3	$120.69	8.410%	$130.84	$130.84	$130.85	$130.80
Purchase #4	$176.25	3.110%	$181.7314	$181.73	$181.75	$181.70
Purchase #5	$168.32	11.108%	$187.017	$187.02	$187.00	$187.00
Purchase #6	$245.79	7.332%	$263.8113	$263.81	$263.80	$263.80
Purchase #7	$61.96	4.130%	$64.5189	$64.52	$64.50	$64.50
7 purchase totals =	$991.50		$1,066.6314	$1,066.64	$1,066.60	$1,066.50