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	$48.54	10.146%	$53.4649	$53.46	$53.45	$53.50
Purchase #2	$242.71	10.519%	$268.2407	$268.24	$268.25	$268.20
Purchase #3	$96.86	6.449%	$103.1065	$103.11	$103.10	$103.10
Purchase #4	$129.53	9.321%	$141.6035	$141.60	$141.60	$141.60
Purchase #5	$237.48	11.850%	$265.6214	$265.62	$265.60	$265.60
Purchase #6	$54.76	12.269%	$61.4785	$61.48	$61.50	$61.50
Purchase #7	$39.39	13.326%	$44.6391	$44.64	$44.65	$44.60
7 purchase totals =	$849.27		$938.1546	$938.15	$938.15	$938.10