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	$139.83	7.292%	$150.0264	$150.03	$150.05	$150.00
Purchase #2	$134.40	6.425%	$143.0352	$143.04	$143.05	$143.00
Purchase #3	$249.75	3.626%	$258.8059	$258.81	$258.80	$258.80
Purchase #4	$131.45	8.273%	$142.3249	$142.32	$142.30	$142.30
Purchase #5	$234.89	3.633%	$243.4236	$243.42	$243.40	$243.40
Purchase #6	$89.51	4.496%	$93.5344	$93.53	$93.55	$93.50
Purchase #7	$91.50	8.130%	$98.939	$98.94	$98.95	$98.90
7 purchase totals =	$1,071.33		$1,130.0894	$1,130.09	$1,130.10	$1,129.90