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	$142.31	10.755%	$157.6154	$157.62	$157.60	$157.60
Purchase #2	$38.45	12.535%	$43.2697	$43.27	$43.25	$43.30
Purchase #3	$248.39	7.164%	$266.1847	$266.18	$266.20	$266.20
Purchase #4	$106.28	9.270%	$116.1322	$116.13	$116.15	$116.10
Purchase #5	$155.98	6.147%	$165.5681	$165.57	$165.55	$165.60
Purchase #6	$207.96	12.555%	$234.0694	$234.07	$234.05	$234.10
Purchase #7	$78.40	6.562%	$83.5446	$83.54	$83.55	$83.50
7 purchase totals =	$977.77		$1,066.3841	$1,066.38	$1,066.35	$1,066.40