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	$139.61	4.799%	$146.3099	$146.31	$146.30	$146.30
Purchase #2	$86.46	3.800%	$89.7455	$89.75	$89.75	$89.70
Purchase #3	$215.96	12.131%	$242.1581	$242.16	$242.15	$242.20
Purchase #4	$57.57	6.276%	$61.1831	$61.18	$61.20	$61.20
Purchase #5	$61.29	11.862%	$68.5602	$68.56	$68.55	$68.60
Purchase #6	$184.89	12.752%	$208.4672	$208.47	$208.45	$208.50
Purchase #7	$150.96	4.400%	$157.6022	$157.60	$157.60	$157.60
7 purchase totals =	$896.74		$974.0262	$974.03	$974.00	$974.10