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	$228.62	11.746%	$255.4737	$255.47	$255.45	$255.50
Purchase #2	$148.53	13.209%	$168.1493	$168.15	$168.15	$168.10
Purchase #3	$89.40	13.462%	$101.435	$101.44	$101.45	$101.40
Purchase #4	$19.65	9.211%	$21.46	$21.46	$21.45	$21.50
Purchase #5	$192.88	12.217%	$216.4441	$216.44	$216.45	$216.40
Purchase #6	$220.47	8.206%	$238.5618	$238.56	$238.55	$238.60
Purchase #7	$10.31	12.816%	$11.6313	$11.63	$11.65	$11.60
7 purchase totals =	$909.86		$1,013.1552	$1,013.15	$1,013.15	$1,013.10