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	$187.77	4.597%	$196.4018	$196.40	$196.40	$196.40
Purchase #2	$59.37	5.831%	$62.8319	$62.83	$62.85	$62.80
Purchase #3	$11.27	5.481%	$11.8877	$11.89	$11.90	$11.90
Purchase #4	$207.63	6.285%	$220.6795	$220.68	$220.70	$220.70
Purchase #5	$117.58	6.439%	$125.151	$125.15	$125.15	$125.20
Purchase #6	$102.73	9.846%	$112.8448	$112.84	$112.85	$112.80
Purchase #7	$28.25	10.699%	$31.2725	$31.27	$31.25	$31.30
7 purchase totals =	$714.60		$761.0692	$761.06	$761.10	$761.10