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	$214.43	11.407%	$238.89	$238.89	$238.90	$238.90
Purchase #2	$45.40	3.420%	$46.9527	$46.95	$46.95	$47.00
Purchase #3	$240.90	10.816%	$266.9557	$266.96	$266.95	$267.00
Purchase #4	$240.52	7.648%	$258.915	$258.92	$258.90	$258.90
Purchase #5	$50.36	12.517%	$56.6636	$56.66	$56.65	$56.70
Purchase #6	$94.51	8.275%	$102.3307	$102.33	$102.35	$102.30
Purchase #7	$81.61	10.583%	$90.2468	$90.25	$90.25	$90.20
7 purchase totals =	$967.73		$1,060.9545	$1,060.96	$1,060.95	$1,061.00