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	$101.58	4.175%	$105.821	$105.82	$105.80	$105.80
Purchase #2	$154.71	13.340%	$175.3483	$175.35	$175.35	$175.30
Purchase #3	$9.73	9.587%	$10.6628	$10.66	$10.65	$10.70
Purchase #4	$182.81	11.844%	$204.462	$204.46	$204.45	$204.50
Purchase #5	$145.65	7.745%	$156.9306	$156.93	$156.95	$156.90
Purchase #6	$183.37	7.390%	$196.921	$196.92	$196.90	$196.90
Purchase #7	$207.31	3.866%	$215.3246	$215.32	$215.30	$215.30
7 purchase totals =	$985.16		$1,065.4703	$1,065.46	$1,065.40	$1,065.40