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	$169.66	7.839%	$182.9596	$182.96	$182.95	$183.00
Purchase #2	$126.35	10.455%	$139.5599	$139.56	$139.55	$139.60
Purchase #3	$89.86	12.207%	$100.8292	$100.83	$100.85	$100.80
Purchase #4	$41.59	8.795%	$45.2478	$45.25	$45.25	$45.20
Purchase #5	$160.91	5.777%	$170.2058	$170.21	$170.20	$170.20
Purchase #6	$175.36	3.364%	$181.2591	$181.26	$181.25	$181.30
Purchase #7	$158.72	10.200%	$174.9094	$174.91	$174.90	$174.90
7 purchase totals =	$922.45		$994.9708	$994.98	$994.95	$995.00