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	$71.48	3.212%	$73.7759	$73.78	$73.80	$73.80
Purchase #2	$36.49	13.778%	$41.5176	$41.52	$41.50	$41.50
Purchase #3	$123.42	6.467%	$131.4016	$131.40	$131.40	$131.40
Purchase #4	$138.91	7.197%	$148.9074	$148.91	$148.90	$148.90
Purchase #5	$189.78	13.486%	$215.3737	$215.37	$215.35	$215.40
Purchase #6	$36.86	13.357%	$41.7834	$41.78	$41.80	$41.80
Purchase #7	$154.82	9.755%	$169.9227	$169.92	$169.90	$169.90
7 purchase totals =	$751.76		$822.6823	$822.68	$822.65	$822.70