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	$99.93	11.803%	$111.7247	$111.72	$111.70	$111.70
Purchase #2	$184.60	7.394%	$198.2493	$198.25	$198.25	$198.20
Purchase #3	$21.85	13.629%	$24.8279	$24.83	$24.85	$24.80
Purchase #4	$139.27	3.719%	$144.4495	$144.45	$144.45	$144.40
Purchase #5	$56.31	5.471%	$59.3907	$59.39	$59.40	$59.40
Purchase #6	$111.49	12.194%	$125.0851	$125.09	$125.10	$125.10
Purchase #7	$72.72	11.860%	$81.3446	$81.34	$81.35	$81.30
7 purchase totals =	$686.17		$745.0718	$745.07	$745.10	$744.90