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	$86.75	13.797%	$98.7189	$98.72	$98.70	$98.70
Purchase #2	$26.69	9.684%	$29.2747	$29.27	$29.25	$29.30
Purchase #3	$118.70	7.752%	$127.9016	$127.90	$127.90	$127.90
Purchase #4	$168.60	4.150%	$175.5969	$175.60	$175.60	$175.60
Purchase #5	$139.87	11.859%	$156.4572	$156.46	$156.45	$156.50
Purchase #6	$172.97	12.164%	$194.0101	$194.01	$194.00	$194.00
Purchase #7	$185.92	4.402%	$194.1042	$194.10	$194.10	$194.10
7 purchase totals =	$899.50		$976.0636	$976.06	$976.00	$976.10