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	$79.84	7.360%	$85.7162	$85.72	$85.70	$85.70
Purchase #2	$98.44	4.711%	$103.0775	$103.08	$103.10	$103.10
Purchase #3	$97.83	7.477%	$105.1447	$105.14	$105.15	$105.10
Purchase #4	$210.91	5.794%	$223.1301	$223.13	$223.15	$223.10
Purchase #5	$224.83	13.700%	$255.6317	$255.63	$255.65	$255.60
Purchase #6	$105.26	3.632%	$109.083	$109.08	$109.10	$109.10
Purchase #7	$129.81	6.167%	$137.8154	$137.82	$137.80	$137.80
7 purchase totals =	$946.92		$1,019.5986	$1,019.60	$1,019.65	$1,019.50