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	$131.29	10.258%	$144.7577	$144.76	$144.75	$144.80
Purchase #2	$148.42	9.747%	$162.8865	$162.89	$162.90	$162.90
Purchase #3	$212.34	5.146%	$223.267	$223.27	$223.25	$223.30
Purchase #4	$71.49	13.851%	$81.3921	$81.39	$81.40	$81.40
Purchase #5	$230.85	12.565%	$259.8563	$259.86	$259.85	$259.90
Purchase #6	$217.54	8.289%	$235.5719	$235.57	$235.55	$235.60
Purchase #7	$134.96	11.342%	$150.2672	$150.27	$150.25	$150.30
7 purchase totals =	$1,146.89		$1,257.9987	$1,258.01	$1,257.95	$1,258.20