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	$199.59	10.872%	$221.2894	$221.29	$221.30	$221.30
Purchase #2	$224.36	10.871%	$248.7502	$248.75	$248.75	$248.80
Purchase #3	$90.75	9.115%	$99.0219	$99.02	$99.00	$99.00
Purchase #4	$142.45	11.484%	$158.809	$158.81	$158.80	$158.80
Purchase #5	$63.97	13.284%	$72.4678	$72.47	$72.45	$72.50
Purchase #6	$109.79	12.326%	$123.3227	$123.32	$123.30	$123.30
Purchase #7	$105.93	7.400%	$113.7688	$113.77	$113.75	$113.80
7 purchase totals =	$936.84		$1,037.4298	$1,037.43	$1,037.35	$1,037.50