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	$151.48	3.188%	$156.3092	$156.31	$156.30	$156.30
Purchase #2	$75.55	10.872%	$83.7638	$83.76	$83.75	$83.80
Purchase #3	$94.80	9.789%	$104.08	$104.08	$104.10	$104.10
Purchase #4	$119.40	3.419%	$123.4823	$123.48	$123.50	$123.50
Purchase #5	$120.39	11.681%	$134.4528	$134.45	$134.45	$134.50
Purchase #6	$150.75	13.606%	$171.261	$171.26	$171.25	$171.30
Purchase #7	$182.84	4.620%	$191.2872	$191.29	$191.30	$191.30
7 purchase totals =	$895.21		$964.6363	$964.63	$964.65	$964.80