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	$92.86	13.201%	$105.1184	$105.12	$105.10	$105.10
Purchase #2	$134.79	6.454%	$143.4893	$143.49	$143.50	$143.50
Purchase #3	$46.84	10.736%	$51.8687	$51.87	$51.85	$51.90
Purchase #4	$247.46	13.349%	$280.4934	$280.49	$280.50	$280.50
Purchase #5	$228.75	4.240%	$238.449	$238.45	$238.45	$238.40
Purchase #6	$138.61	10.511%	$153.1793	$153.18	$153.20	$153.20
Purchase #7	$47.96	5.622%	$50.6563	$50.66	$50.65	$50.70
7 purchase totals =	$937.27		$1,023.2544	$1,023.26	$1,023.25	$1,023.30