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	$221.94	10.649%	$245.5744	$245.57	$245.55	$245.60
Purchase #2	$11.30	4.198%	$11.7744	$11.77	$11.75	$11.80
Purchase #3	$43.40	6.680%	$46.2991	$46.30	$46.30	$46.30
Purchase #4	$143.79	4.612%	$150.4216	$150.42	$150.40	$150.40
Purchase #5	$191.43	7.816%	$206.3922	$206.39	$206.40	$206.40
Purchase #6	$96.48	5.652%	$101.933	$101.93	$101.95	$101.90
Purchase #7	$134.46	12.192%	$150.8534	$150.85	$150.85	$150.90
7 purchase totals =	$842.80		$913.2481	$913.23	$913.20	$913.30