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	$149.78	3.873%	$155.581	$155.58	$155.60	$155.60
Purchase #2	$192.88	7.254%	$206.8715	$206.87	$206.85	$206.90
Purchase #3	$96.59	8.708%	$105.0011	$105.00	$105.00	$105.00
Purchase #4	$41.45	9.734%	$45.4847	$45.48	$45.50	$45.50
Purchase #5	$6.43	7.591%	$6.9181	$6.92	$6.90	$6.90
Purchase #6	$183.32	7.296%	$196.695	$196.70	$196.70	$196.70
Purchase #7	$82.32	11.566%	$91.8411	$91.84	$91.85	$91.80
7 purchase totals =	$752.77		$808.3925	$808.39	$808.40	$808.40