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	$143.50	11.584%	$160.123	$160.12	$160.10	$160.10
Purchase #2	$141.62	9.343%	$154.8516	$154.85	$154.85	$154.90
Purchase #3	$79.95	7.622%	$86.0438	$86.04	$86.05	$86.00
Purchase #4	$93.43	11.642%	$104.3071	$104.31	$104.30	$104.30
Purchase #5	$80.65	10.415%	$89.0497	$89.05	$89.05	$89.00
Purchase #6	$182.61	8.631%	$198.3711	$198.37	$198.35	$198.40
Purchase #7	$102.75	6.710%	$109.6445	$109.64	$109.65	$109.60
7 purchase totals =	$824.51		$902.3908	$902.38	$902.35	$902.30