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	$141.39	8.106%	$152.8511	$152.85	$152.85	$152.90
Purchase #2	$100.88	13.551%	$114.5502	$114.55	$114.55	$114.60
Purchase #3	$20.84	4.701%	$21.8197	$21.82	$21.80	$21.80
Purchase #4	$211.56	10.845%	$234.5037	$234.50	$234.50	$234.50
Purchase #5	$126.81	11.548%	$141.454	$141.45	$141.45	$141.50
Purchase #6	$181.33	8.494%	$196.7322	$196.73	$196.75	$196.70
Purchase #7	$148.60	9.440%	$162.6278	$162.63	$162.65	$162.60
7 purchase totals =	$931.41		$1,024.5387	$1,024.53	$1,024.55	$1,024.60