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	$72.46	7.837%	$78.1387	$78.14	$78.15	$78.10
Purchase #2	$102.52	6.600%	$109.2863	$109.29	$109.30	$109.30
Purchase #3	$212.98	11.335%	$237.1213	$237.12	$237.10	$237.10
Purchase #4	$249.69	12.208%	$280.1722	$280.17	$280.15	$280.20
Purchase #5	$97.79	4.755%	$102.4399	$102.44	$102.45	$102.40
Purchase #6	$150.49	9.631%	$164.9837	$164.98	$165.00	$165.00
Purchase #7	$79.59	8.298%	$86.1944	$86.19	$86.20	$86.20
7 purchase totals =	$965.52		$1,058.3365	$1,058.33	$1,058.35	$1,058.30