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	$210.88	13.847%	$240.0806	$240.08	$240.10	$240.10
Purchase #2	$34.87	13.856%	$39.7016	$39.70	$39.70	$39.70
Purchase #3	$195.63	11.596%	$218.3153	$218.32	$218.30	$218.30
Purchase #4	$83.65	6.749%	$89.2955	$89.30	$89.30	$89.30
Purchase #5	$123.64	3.159%	$127.5458	$127.55	$127.55	$127.50
Purchase #6	$78.59	4.460%	$82.0951	$82.10	$82.10	$82.10
Purchase #7	$215.79	5.459%	$227.57	$227.57	$227.55	$227.60
7 purchase totals =	$943.05		$1,024.6039	$1,024.62	$1,024.60	$1,024.60