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	$159.54	7.425%	$171.3858	$171.39	$171.40	$171.40
Purchase #2	$207.45	4.112%	$215.9803	$215.98	$216.00	$216.00
Purchase #3	$185.91	13.705%	$211.389	$211.39	$211.40	$211.40
Purchase #4	$78.35	4.423%	$81.8154	$81.82	$81.80	$81.80
Purchase #5	$216.52	13.340%	$245.4038	$245.40	$245.40	$245.40
Purchase #6	$97.79	6.811%	$104.4505	$104.45	$104.45	$104.50
Purchase #7	$99.92	13.183%	$113.0925	$113.09	$113.10	$113.10
7 purchase totals =	$1,045.48		$1,143.5173	$1,143.52	$1,143.55	$1,143.60