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	$50.73	12.394%	$57.0175	$57.02	$57.00	$57.00
Purchase #2	$86.71	11.445%	$96.634	$96.63	$96.65	$96.60
Purchase #3	$119.84	7.583%	$128.9275	$128.93	$128.95	$128.90
Purchase #4	$202.32	9.405%	$221.3482	$221.35	$221.35	$221.30
Purchase #5	$214.66	11.588%	$239.5348	$239.53	$239.55	$239.50
Purchase #6	$196.97	4.306%	$205.4515	$205.45	$205.45	$205.50
Purchase #7	$90.83	11.112%	$100.923	$100.92	$100.90	$100.90
7 purchase totals =	$962.06		$1,049.8365	$1,049.83	$1,049.85	$1,049.70