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	$47.75	7.512%	$51.337	$51.34	$51.35	$51.30
Purchase #2	$244.62	8.139%	$264.5296	$264.53	$264.55	$264.50
Purchase #3	$172.56	10.858%	$191.2966	$191.30	$191.30	$191.30
Purchase #4	$63.41	5.483%	$66.8868	$66.89	$66.90	$66.90
Purchase #5	$111.85	5.657%	$118.1774	$118.18	$118.20	$118.20
Purchase #6	$182.81	8.574%	$198.4841	$198.48	$198.50	$198.50
Purchase #7	$143.27	9.196%	$156.4451	$156.45	$156.45	$156.40
7 purchase totals =	$966.27		$1,047.1566	$1,047.17	$1,047.25	$1,047.10