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	$229.75	4.797%	$240.7711	$240.77	$240.75	$240.80
Purchase #2	$57.64	9.333%	$63.0195	$63.02	$63.00	$63.00
Purchase #3	$156.59	7.332%	$168.0712	$168.07	$168.05	$168.10
Purchase #4	$111.64	7.419%	$119.9226	$119.92	$119.90	$119.90
Purchase #5	$129.38	6.495%	$137.7832	$137.78	$137.80	$137.80
Purchase #6	$229.77	10.792%	$254.5668	$254.57	$254.55	$254.60
Purchase #7	$133.90	6.591%	$142.7253	$142.73	$142.75	$142.70
7 purchase totals =	$1,048.67		$1,126.8597	$1,126.86	$1,126.80	$1,126.90