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	$125.77	9.344%	$137.5219	$137.52	$137.50	$137.50
Purchase #2	$215.96	5.301%	$227.408	$227.41	$227.40	$227.40
Purchase #3	$211.88	13.191%	$239.8291	$239.83	$239.85	$239.80
Purchase #4	$66.46	9.288%	$72.6328	$72.63	$72.65	$72.60
Purchase #5	$128.41	10.843%	$142.3335	$142.33	$142.35	$142.30
Purchase #6	$55.80	3.725%	$57.8786	$57.88	$57.90	$57.90
Purchase #7	$172.73	5.773%	$182.7017	$182.70	$182.70	$182.70
7 purchase totals =	$977.01		$1,060.3056	$1,060.30	$1,060.35	$1,060.20