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	$62.76	13.341%	$71.1328	$71.13	$71.15	$71.10
Purchase #2	$155.29	5.687%	$164.1213	$164.12	$164.10	$164.10
Purchase #3	$249.97	12.336%	$280.8063	$280.81	$280.80	$280.80
Purchase #4	$178.61	11.256%	$198.7143	$198.71	$198.70	$198.70
Purchase #5	$103.51	11.329%	$115.2366	$115.24	$115.25	$115.20
Purchase #6	$152.71	13.154%	$172.7975	$172.80	$172.80	$172.80
Purchase #7	$47.76	8.681%	$51.906	$51.91	$51.90	$51.90
7 purchase totals =	$950.61		$1,054.7148	$1,054.72	$1,054.70	$1,054.60