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	$190.64	3.481%	$197.2762	$197.28	$197.30	$197.30
Purchase #2	$51.76	5.418%	$54.5644	$54.56	$54.55	$54.60
Purchase #3	$125.34	8.788%	$136.3549	$136.35	$136.35	$136.40
Purchase #4	$205.75	12.463%	$231.3926	$231.39	$231.40	$231.40
Purchase #5	$72.57	8.129%	$78.4692	$78.47	$78.45	$78.50
Purchase #6	$97.53	8.318%	$105.6425	$105.64	$105.65	$105.60
Purchase #7	$201.42	5.172%	$211.8374	$211.84	$211.85	$211.80
7 purchase totals =	$945.01		$1,015.5372	$1,015.53	$1,015.55	$1,015.60