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	$172.61	7.794%	$186.0632	$186.06	$186.05	$186.10
Purchase #2	$238.45	7.410%	$256.1191	$256.12	$256.10	$256.10
Purchase #3	$183.38	3.132%	$189.1235	$189.12	$189.10	$189.10
Purchase #4	$101.69	10.212%	$112.0746	$112.07	$112.05	$112.10
Purchase #5	$75.79	8.205%	$82.0086	$82.01	$82.00	$82.00
Purchase #6	$213.52	11.357%	$237.7695	$237.77	$237.75	$237.80
Purchase #7	$73.34	6.681%	$78.2398	$78.24	$78.25	$78.20
7 purchase totals =	$1,058.78		$1,141.3983	$1,141.39	$1,141.30	$1,141.40