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	$111.42	3.785%	$115.6372	$115.64	$115.65	$115.60
Purchase #2	$72.65	4.242%	$75.7318	$75.73	$75.75	$75.70
Purchase #3	$204.71	13.716%	$232.788	$232.79	$232.80	$232.80
Purchase #4	$164.97	12.379%	$185.3916	$185.39	$185.40	$185.40
Purchase #5	$90.94	9.326%	$99.4211	$99.42	$99.40	$99.40
Purchase #6	$85.92	5.787%	$90.8922	$90.89	$90.90	$90.90
Purchase #7	$247.83	3.850%	$257.3715	$257.37	$257.35	$257.40
7 purchase totals =	$978.44		$1,057.2334	$1,057.23	$1,057.25	$1,057.20