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	$41.51	13.470%	$47.1014	$47.10	$47.10	$47.10
Purchase #2	$74.39	10.240%	$82.0075	$82.01	$82.00	$82.00
Purchase #3	$98.76	4.815%	$103.5153	$103.52	$103.50	$103.50
Purchase #4	$124.42	5.521%	$131.2892	$131.29	$131.30	$131.30
Purchase #5	$39.92	9.242%	$43.6094	$43.61	$43.60	$43.60
Purchase #6	$206.54	3.416%	$213.5954	$213.60	$213.60	$213.60
Purchase #7	$61.79	6.249%	$65.6513	$65.65	$65.65	$65.70
7 purchase totals =	$647.33		$686.7695	$686.78	$686.75	$686.80